This document asks to find the expected value of the random variable g(x1, x2) = x1 + x2 given that two random variables have a joint density of f(x1, x2) = x1x2 for 0 < x1, x2 < 1 and 0 otherwise. To solve this, the expected value E[g] is defined as the double integral of g(x1, x2) multiplied by the joint density f(x1, x2) over the domain of x1 and x2.