Unable to resolve dependency for 'app@debugcompileClasspath' Couldn’t resolve android studio

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Soultion for all 11 errors
1. Android Studio: Re-download dependencies and sync undertaking error
2. gradle-sync-error-in-android-studio-when-importing-project
3. Android Gradle sync failed (import undertaking from github)
4. Unable to resolve all dependencies in android studio 3.0
5. Unable to resolve dependency for ‘:app@debug/compileClasspath
6. Unable to resolve dependency for… Couldn’t resolve undertaking :library. Required by: undertaking :app
7. Unable to resolve dependency for ‘:app@debug/compileClasspath’: Couldn’t resolve com.android.assist:appcompat-v7:26.1.0.
8 .Importing Android Initiatives into Android Studio
9.android studio importing undertaking error
10.Android Gradle sync failed (import undertaking from github)
11.re-download dependencies and sync undertaking (requires community) android studio

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