describing a language with a regular expression

Question

How can i write a regular expression to describe this language :

Answer 1

the following should do the job:

[0-1]{2}([0-1]{5})*

you first take 0 or 1 twice and then you add a block of five characters (0 or 1) an arbitrary number of times

Answer 2

You're trying to build a regex which matches zero or more occurences of (five [01]s), followed by two more [01]s.

In other words: ([0-1]{5})*[01]{2}