find a regular expression

Question

find a regular expression for w such that it does not contain $ aab $ , where w is the strings of $a$'s and $b$'s .

ans: I know how to draw the same question with $ aab $ , but cant understand how to proceed for this question.

Answer 1

There is an algorithm for converting a FA into a RE. Since you said you can draw the FA, why not apply that algorithm?