Since we are given the function, we can simply plug in the x as 9. So we get 50(0.952)9. Solving this, we get 450(.952) and this is about 428. SO our answer is a) about 428 feral cats.
Try out each of the situations. It can't be A, since the 0.9 is less than 1, so it has to be decreasing. This leaves only B and C. Since decreasing by 90 percent is the same as multiplying by 10 percent, the only possible answer left is B.