Solve for y in the second equation, so you have y= -3x + 12. Now plug that in for y in the first equation: 5x + 3( -3x +12) = 28. Now simplify: 5x + -9x + 36 = 28: -4x = -8; so x = 2. Now plug x=2 into either equation to solve for y: 3(2) + y = 12; 6 + y = 12; so y = 6
