[Haskell-beginners] Can't remove old haskell

I've followed the steps here https://www.haskell.org/platform/linux.html#linux-generic; however, it doesn't replace or supercede an older version of ghci from my Ubuntu 18.04: 12:47:02:~$ which ghci /opt/ghc/8.0.2/bin/ghci 12:47:14:~$ ghci --version The Glorious Glasgow Haskell Compilation System, version 8.0.2 I've tried various removes, but to no avail. The newer version is on my system: 12:50:32:/usr/local/haskell/ghc-8.4.2-x86_64/bin$ ./ghci --version The Glorious Glasgow Haskell Compilation System, version 8.4.2 But I don't know what to do about this old "default" version. LB