Hi ;]
4 ≤ -3x - 1 ≤ 9
-3x - 1 ≥ 4 / + 1
-3x ≥ 5 / : (-3)
x ≥ -⁵/₃
-3x - 1 ≤ 9 / + 1
-3x ≤ 10 / : (-3)
x ≤ -¹⁰/₃
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