1. The problem statement, all variables and given/known data If X1 has mean -3 and variance 2 while X2 has mean 5 and variance 4 and the two are independent find a) E(X1 - X2) b) Var(X1 - X2) 3. The attempt at a solution I am not very clear on what I am supposed to be doing for this problem. I don't fully understand this expectation value concept. Can someone help explain what they are asking me to do or give me a hint on how to get started please? Here is what I did so far but I don't know if its worth anything they are independent so my book says the covariance is 0 so E[(X1 - μ1)(X2 - μ2)] = 0 E[(X1 + 3)(X2 - 5)] = 0 E[X1X2 - 5X1 + 3X2 -15] = 0 I think that is equal to this but I may be wrong: E[X1X2] - 5E[X1] + 3 E[X2] - 15 = 0 I don't know what to do from here though. Am I on the right track at all?