How can i prove the following? [duplicate]

I want to prove that if $5\mid(a+11)$ and $5\mid(16-b)$ then $5\mid(a+b)$

Can you help me?

Thanks in advance PS. It's urgent!

-
Exact duplicate of said question from 14 hours ago. –  Math Gems Apr 2 '13 at 18:14
@amWhy Yes, the point of my comment was to say more than the the terse automatic message, so that voters have further info on which to base their decision. –  Math Gems Apr 2 '13 at 18:18
Hint: $$a + b = (a + 11) - (16 - b) + 5$$