ok. Let's do this! x - (4x - 7) = 5x - (x + 21) Distribute the minus into the parenthesis and then get x -4x +7 = 5x -x -21(combine like terms) x -4x +7 = 4x -21(combine like terms) -3x +7 = 4x -21(Add 3x to both sides) +3x +3x 7 = 7x -21(Add 21 to both sides) +21 +21 28 = 7x(Divide 7 from both sides) 4 = x The answer is x = 4