1. The problem statement, all variables and given/known data Calculate the volume of the body that is bounded by the planes: x+y-z = 0 y-z = 0 y+z = 0 x+y+z = 2 2. Relevant equations 3. The attempt at a solution I made a variable substitution u = y+z v = y-z w = x which gave me the new boundaries u+w = 2 v+w = 0 v = 0 u = 0 Problem is, I must have slept late the day they taught this is class. What do I do to determine which way these inequalities go?!?