According to the answer here from Stack Overflow:
Temporary fix: append nomodeset xforcevesa at the end of the line containing kernel during boot time at the GRUB menu. During boot press E to edit. While on the line containing kernel press E again, append nomodeset xforcevesa at the end, press enter, then press B to boot.
Permanent fix: read the answer here....
Need to add emulator -"$ANDROID_INSTALLATION/Android/Sdk/emulator" to your $PATH variable.
after adding the path variable you will need to restart the terminal session.
and / or you can permanently add the path variable by editing the bashrc/profile file depending your distribution.