Answer :

3a=9

firstly, you will need to divide each side of the equal sign by 3.

3a/3=9/3

Once you divide, you end up with a=3

Hope this helped! 
you divide 3 from both sides

and the answer is a=3
because 3 divided by 3 is 0
and you don't have to write it
and then 9 divided by 3 is 3
so replace the 9 with 3 and it gives you
a=3