As mentioned in the earlier comments, the problem might be because of slow internet connection, just to add more details, you need to download all the problematic file which you get in the logs, in my case they were (emulator-windows_x.zip and x86-30_r09.zip) and place them in the respective sub-folders (PackageOperation02 or PackageOperation05 ..) present in .tmp folder located under andriod-sdk root folder and retrigger the sdk installation from Andriod studio.