Brainliest! Fill in the blank with an appropriate inequality sign.
(a) If x < 7, then x − 3 __ 4.
(b) If x ≤ 7, then 3x __ 21.
(c) If x ≥ 6, then −3x __ −18.
(d) If x < −6, then −x __ 6.