Question

y varies jointly with p and q. When p = 4 and q = 5, y = 60. Find y when p = 5 and q = 8.

Answer 1

I think joint variation goes by y = kxz, or in your case, y = kpq.

Answer 2

First plug in p = 4, q = 5, and y = 60 to find the k. Then plug in k, q = 8 and p = 5 to find y.