Tom K. answered 03/18/21
Knowledgeable and Friendly Math and Statistics Tutor
Melissa, I have already answered nearly the exactly same problem for you.
10 - 2 = 8
f(x,y) = 1/8 * 1/8 = 1/64 on [2, 10] x [2, 10]
P(X + Y) >= 18, as 10 + 10 = 20, is 1/2 * 2^2 * 1/64 = 1/32
See other problem for details.