Which best describes the solution set of the compound inequality below?


2 + x ≤ 3x – 6 ≤ 12

a: 4 ≤ x ≤ 9
b: 4 ≤ x ≤ 6
c: –2 ≤ x ≤ 2
d: –2 ≤ x ≤ 3