15.
a) 2x + 2 = -7x - 21 + 3•3x - 15 - 5
2x + 2 = 9x - 7x - 41
2x + 2 = 2x - 41
2x = 2x - 43
2x + 2 - 2 = 2x - 41 - 2
2x - 2x = 2x - 2x - 43
x = -43
b) 14 + 3•3x - 3 = 3•7x - 9 - 10
9x + 11 = 21x - 19
9x = 21x - 30
9x + 11 - 11 = 21x - 19 - 11
-12x = -30
9x - 21x = 21x - 21x - 30
x = -5 / -2
c) 14 + 2(3-2(x-3)) / 2 = 37
28 + 2(3-2(x-3)) = 74
2 • 14 + 2•2(3-2(x-3)) / 2 = 2 • 37
28 + 2(-2x + 6 + 3) = 74
28 + -2 • 2x + 18 = 74
4(-x - 7) = 0
x = -7.
