Answer:
D. -6 < x ≤ -3.
Step-by-step explanation:
21 ≤ -3(x - 4) < 30
-3(x - 4) < 30
-3x + 12 < 30
-3x < 18
x > -6. (Note: the sign flips when you divide by a negative).
-3(x - 4) ≥ 21
-3x + 12 ≥ 21
-3x ≥ 9
x ≤ -3.
