Note: the real problem is integrating e^(x + y) dydx where 0<= y <= ln2 and 0 <= x <= ln3. My solution manual says that the inner integral is e^x. I just can't see how you get e^x from integral e^(x + y) dy = e^x with the given limits (0 <= y <= ln2). I replaced x with 2 since x is constant in the inner integral on my original post.