Bonjour,
1) 1/8
2) -140/210 = -2/3
3) -3/5 + 11/10 = -6/10 + 11/10 = 5/10 = 1/2
4) 32/75 × 55/24 = (8×4×11×5)/(15×5×3×8) = 44/45
5) 8/3 ÷ 4 = 8/3 × 1/4 = 8/12 = 2/3
6) 24 h × 1/6 = 4 h
7) économies × 4/5 = 350
donc : économies = 350 ÷ 4/5 = 437,5
8) 200 × 1/4 = 50
200 - 50 = 150
150 × 2/3 = 100
150 - 100 = 50
50 - 20 = 30
30 × 4/5 = 24
30 - 24 = 6