Réponse :
1. (x + 1)/3 ≤ (2x - 2)/ 5
5 × (x + 1)/ 3×5 ≤ 3× (2x - 2)/ 5 × 3
5(x + 1) 15 ≤ 3(2x - 2)/15
5(x + 1) ≤ 3(2x - 2)
5x + 5 ≤ 6x - 6
5x -6x ≤ -6 - 5
-x ≤ -11
x ≥ 11
2. -2x + 1/3 < x - 1/4
-2x - x < - 1/4 - 1/3
-3x < -3/12 - 4/12
-3x < -7/12
3x > 7/12
x > 7/36
3. 2(x/3 - 5) ≥ x + 3/4
2x/3 - 10 ≥ x + 3/4
2x/3 - x ≥ 3/4 +10
2x/3 - 3x/3 ≥ 3/4 + 40/4
-x/3 ≥ 43/4
-x ≥ 43 × 3/4
- x ≥ 129/4
x ≤ -129/4
