Réponse :

bonjour,

A = 5/7 + 2×4 /7×5

A =5/7  + 8/35

A =  5×5 + 8 / 35

A = 25 + 8 /35

A = 33/35

B = 1×3 + 1×5 / 15 ÷ 2×4 - 3×5 / 12

B = 3 + 5 /15 ÷ 8 - 15 /12

B = 8/5 ÷ - 7/12

B = 8/5 × - 12/7

B = - 96/35

C = - 8/5 + - 2/3 + 5/2

C = - 8×3×2 + - 2×5×2 + 5× 5× 3 / 5×3×2

C = - 48 - 20 + 75 / 30

C = 7/30

Explications étape par étape :