Like: used to compare two nouns.
Gita and Sita, as their mother Reema, are extremely smart. - Incorrect
Gita and Sita, like their mother Reema, are extremely smart. - Correct
As: used to compare two clauses.
Just like swimming is good exercise, running is a way to burn calories. - Incorrect
Just as swimming is good exercise, running is a way to burn calories. - Correct
Note : Do not use like to mean for example.
Gmat Sentence Correction Example - Click on the link below and see sentence number 38
http://gmatsentencecorrection.blogspot.com/
