a) −3/8 × x/9 = 2/3
x/9 = 2/3 ÷ −3/8
x/9 = 2/3 × −8/3
x = −16/9 × 9
x = −16
[Vérification : −3/8 × −16/9 = −1/1 × −2/3
= 2/3]
b) 3/−2 ÷ x/7 = −21/10
−3/2 ÷ −21/10 = x/7
3/2 × 10/21 = x/7
1/1 × 5/7 × 7 = x
x = 5
[Vérification : 3/−2 ÷ 5/7 = −3/2 × 7/5
= −21/10]
