Okay, this is a case of substitution: 3x + y = 13 correct? -3x -3x So: y = 13 - 3x So: 3x +(13-3x)=13 and this is interchangeable, so x and y = all positive numbers aka. 6x + 2(13-3x) = 26 it does not matter what numbers x and y are as long as they positive
