65. This is a question about the binomial expansion.

You need to know that

(a+b)^n = sum_{r=0 to n} [n!/((n-r)! r!] a^{n-r} b^r

so in your case a=x^3, b=-y^2, n=20, and as you are asked for the 8-th

term r=7.

So the 8-th term is:

[20!/(13! 7!)] (x^3)^13 (-y^2)^7

which is answer D.

RonL