12-6 (w-3) = 3 (-5-3w) + 21

w = - 8

Step-by-step explanation:

12-6 (w-3) = 3 (-5-3w) + 21 (expand parentheses)

12-6 (w) - (-6) (3) = (3) (-5) - (3) (3w) + 21

12 - 6w + 18 = - 15 - 9w + 21

-6w + 30 = 6 - 9w (add 9w to both sides)

-6w + 30 + 9w = 6

3w + 30 = 6 (subtract 20 from both sides)

3w = 6 - 30

3w = - 24 (divide both sides by 3)

w = - 24 : 3

w = - 8