Question

Solve for x: -3(x - 3) = 21

Answer 1

-3x +9 = 21
-3x = 21 - 9
-3x = 12
x = -(12/3)
x = -4

Answer 2

If you factor the -3 into (x-3) you get -3x + 9 = 21.
(It is a positive 9 because a negative times a negative equals a positive)

-3x + 9 =21
Subtracting 9 from each side, you get:
-3x = 12
Divide each side by -3 and you get:
x = -4.