From what I learned,
もらえる = もらうことが出来る
'can be got'
見える = 見ることが出来る
'can be seen'
This looks like there is some kind of a more general rule for this transformation.
- If there is a pair of such verbs, is the one with ~え~ always meaning ~ことが出来る?
- Is there any rule when can I create a ~え~ verb this way?