Im not sure if it's correct or not, but this is how I solved it:
13ab + 16a - 15av
{Combine like terms, take the sign as well}
13ab - 15ab = -2a^2b^2
and then I believe theres your answer:
-2a^2b^2 + 16a.
You cannot combine anything else b/c there are no other like terms so just leave it be.