1. The problem statement, all variables and given/known data 2. Relevant equations Equation 1: 3x+2y+1/3z=50 Equation 2: x+y+z=100 3. The attempt at a solution I know that the variables go like this: x=5, y=2 and z=93. I solved this combining different variables until I got the right "combination". I have to prove these solutions, any ideas how?