yarnを使ったレスポンシブウェブデザイン作成について

以下のエラーの意味を理解し解決したいです。
現在レスポンシブのWebページを作成中で、ejsとscssを使いコーディングし、パッケージマネジャーはyarnです。

以下のエラーはyarn startでローカルホストを立ち上げた際に出ているものです。

bundle.js:20084 Uncaught Error: Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
ModuleBuildError: Module build failed (from ./node_modules/sass-loader/lib/loader.js):
Error: Node Sass does not yet support your current environment: OS X 64-bit with Unsupported runtime (72)
For more information on which environments are supported please see:
https://github.com/sass/node-sass/releases/tag/v4.11.0
    at module.exports (:8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/node-sass/lib/binding.js:13)
    at Object.<anonymous> (:8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/node-sass/lib/index.js:14)
    at Module._compile (:8080/internal/modules/cjs/loader.js:936)
    at Object.Module._extensions..js (:8080/internal/modules/cjs/loader.js:947)
    at Module.load (:8080/internal/modules/cjs/loader.js:790)
    at Function.Module._load (:8080/internal/modules/cjs/loader.js:703)
    at Module.require (:8080/internal/modules/cjs/loader.js:830)
    at require (:8080/internal/modules/cjs/helpers.js:68)
    at Object.sassLoader (:8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/sass-loader/lib/loader.js:46)
    at :8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/webpack/lib/NormalModule.js:301
    at :8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:367
    at :8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:233
    at runSyncOrAsync (:8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:143)
    at iterateNormalLoaders (:8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:232)
    at Array.<anonymous> (:8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:205)
    at Storage.finished (:8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:43)
    at :8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:79
    at :8080/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/graceful-fs/graceful-fs.js:90
    at FSReqCallback.readFileAfterClose [as oncomplete] (:8080/internal/fs/read_file_context.js:61)
    at Object../src/scss/app.scss (bundle.js:20084)
    at __webpack_require__ (bootstrap:19)
    at Object../src/js/index.js (index.js:3)
    at __webpack_require__ (bootstrap:19)
    at Object.0 (bundle.js:20096)
    at __webpack_require__ (bootstrap:19)
    at bootstrap:83
    at bootstrap:83
./src/scss/app.scss @ bundle.js:20084
__webpack_require__ @ bootstrap:19
./src/js/index.js @ index.js:3
__webpack_require__ @ bootstrap:19
0 @ bundle.js:20096
__webpack_require__ @ bootstrap:19
(anonymous) @ bootstrap:83
(anonymous) @ bootstrap:83
client:162 [WDS] Errors while compiling. Reload prevented.
errors @ client:162
onmessage @ socket.js:41
EventTarget.dispatchEvent @ sockjs.js:170
(anonymous) @ sockjs.js:887
SockJS._transportMessage @ sockjs.js:885
EventEmitter.emit @ sockjs.js:86
WebSocketTransport.ws.onmessage @ sockjs.js:2961
client:168 ./src/js/index.js
Module Error (from ./node_modules/eslint-loader/index.js):

/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/src/js/index.js
  11:1  error  'app' is not defined      no-undef
  11:9  error  'express' is not defined  no-undef

✖ 2 problems (2 errors, 0 warnings)

errors @ client:168
onmessage @ socket.js:41
EventTarget.dispatchEvent @ sockjs.js:170
(anonymous) @ sockjs.js:887
SockJS._transportMessage @ sockjs.js:885
EventEmitter.emit @ sockjs.js:86
WebSocketTransport.ws.onmessage @ sockjs.js:2961
client:168 ./src/scss/app.scss
Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
ModuleBuildError: Module build failed (from ./node_modules/sass-loader/lib/loader.js):
Error: Node Sass does not yet support your current environment: OS X 64-bit with Unsupported runtime (72)
For more information on which environments are supported please see:
https://github.com/sass/node-sass/releases/tag/v4.11.0
    at module.exports (/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/node-sass/lib/binding.js:13:13)
    at Object.<anonymous> (/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/node-sass/lib/index.js:14:35)
    at Module._compile (internal/modules/cjs/loader.js:936:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:947:10)
    at Module.load (internal/modules/cjs/loader.js:790:32)
    at Function.Module._load (internal/modules/cjs/loader.js:703:12)
    at Module.require (internal/modules/cjs/loader.js:830:19)
    at require (internal/modules/cjs/helpers.js:68:18)
    at Object.sassLoader (/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/sass-loader/lib/loader.js:46:72)
    at /Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/webpack/lib/NormalModule.js:301:20
    at /Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:367:11
    at /Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:233:18
    at runSyncOrAsync (/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:143:3)
    at iterateNormalLoaders (/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:232:2)
    at Array.<anonymous> (/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/loader-runner/lib/LoaderRunner.js:205:4)
    at Storage.finished (/Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:43:16)
    at /Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:79:9
    at /Users/mochiji/Desktop/kadai-1/kadai_PC/kadai_LP_1/node_modules/graceful-fs/graceful-fs.js:90:16
    at FSReqCallback.readFileAfterClose [as oncomplete] (internal/fs/read_file_context.js:61:3)
errors @ client:168
onmessage @ socket.js:41
EventTarget.dispatchEvent @ sockjs.js:170
(anonymous) @ sockjs.js:887
SockJS._transportMessage @ sockjs.js:885
EventEmitter.emit @ sockjs.js:86
WebSocketTransport.ws.onmessage @ sockjs.js:2961
client:177 [WDS] Disconnected!
ここより以下は文字制限、重要ではないと思われる？為ひとまず省きます

2KOH

2019/11/19 23:27

エラーが発生するまでの手順を提示してください。具体的には、以下の「不明」の部分を提示してください。 1. Node.js と Yarn をインストールする。 2. 不明 3. yarn start を実行すると、エラーが発生する。エラーメッセージを元に上記の不明の部分の手順を推測することは頑張ればできるかもしれませんが、質問者が提示してくれさえすれば済む話です。