How to find the path to NDK?

Finding your SDK/NDK library path needs information about how you installed them. However, there are two possible solutions to find them

1. Using Android Studio: the possible way to find is using Android Studio. Open your Android Studio Preference (or "File->Settings") > Appearance & Behavior > System Settings > Android SDK. You can find the path to your SDK and NDK, which is in the same directory.

2. Using Terminal: Open Terminal and put the command as below. Hopefully, if ANDROID_HOME environment has been set.

   echo $ANDROID_HOME

My understanding is that now the NDK bundle is being offered via the SDK Manager within Android Studio, it will install into the Android SDK directory as per the other components (platforms, build tools, support repositories, etc.) in the SDK Manager.

You can check the location of the SDK directory itself via Android Studio -> Preferences... -> Appearance & Behavior -> System Settings -> Android SDK -> Android SDK Location field near the top of the panel.

I've customised mine (it's editable) so I'm afraid I don't know what the default is, but if you check the contents of the directory listed in that field then the NDK should be installed into a subdirectory called ndk-bundle.

You can find it on $ANDROID_SDK_PATH/ndk-bundle.
ANDROID_SDK_PATH is your SDK path which I suppose you have set it already.