bonjour, pouvez vous m'aidez svp merci

Salut !

1/4 - 5/12 + 1/3 = 3/12 - 5/12 + 4/12 = 2/12 = 1/6

14/20 × 8/21 = (2×7×2×4)/(2×2×5×3×7) = 4/15

1/3 + 2/3 × 7/5 = 1/3 + 14/15 = 5/15 + 14/15 = 19/15

3 + 3/5 = 15/5 + 3/5 = 18/5

5/4 × 1/3 - 3/4 = 5/12 - 3/4 = 5/12 - 9/12 = -4/12 = (-4×1)/(4×3) = -1/3

3/4 - 5/4 ÷ 10/6 = 3/4 - 5/4 × 6/10 = 3/4 - (5×3×2)/(4×2×5)

                                                     = 3/4 -     3/4

                                                     = 0

6/5 × (1/4 - 1/3) = 6/5 × (3/12 - 4/12) = 6/5 × (-1/12) = (6 × (-1))/(5×2×6)

                                                                                  =  -1/10

5/21 ÷ 15/9 = 5/21 × 9/15 = (5×3×3)/(7×3×5×3) = 1/7

3/4 - 1/15 - 7/20 = 45/60 - 4/60 - 21/60 = 20/60 = 1/3