13-5-13+3a?

Question

whats the answer and how do you do it?

Answer 1

13-5-13+3a

Step 1: Combine like terms.
(13-5-13) + 3a
13 - 5 = 8. 8 - 13 = -5
-5 + 3a (solution!)

Without knowing the value of a, or setting the equation equal to something, this is the most you can do.