Consider and

If has a term and a term, determine ...

I have tried to solve this several different ways, however I have not yet reached the correct answer. It would be so helpful if you could show me how to solve this!!

The x^3 term will be ax^2*3x + -5x*bx^2 = (3a-5b)x^3

so 3a-5b = 20

Now find x^2 term and then solve simultaneously.