4x-6y-7x+8 combine like terms: -3x-6y+8 If all you want to do is simplify, then that is the final answer. However if we want to evaluate that when x=5 and y=2, we substitute (5) in place of x and (2) in place of y -3x-6y+8 -3(5)-6(2)+8 Then do all the operations: -15-12+8 -19