Answer:
(-∞, -12), (2, ∞)
or
(-∞, -12) U (2, ∞)
Explanation:
|3x + 15| > 21, |3x + 15| < -21
3x + 15 > 21, 3x + 15 < - 21
-15 -15 -15 -15
------------------ -------------------
3x > 6 3x < - 36
÷3 ÷3 ÷3 ÷3
------------ ------------------
x > 2 x < -12
(-∞, -12), (2, ∞)
or
(-∞, -12) U (2, ∞)
I hope this helps!