Bonjour :
(-)×(-) = (+)
(-)×(+) = (-)
A = 2/7 - 3/7 × 14/9
A = 2/7 - 3×14/7×9
A = 2/7 - 3×7×2/7×3×3
A = 5/7 - 2/3
A = 15/21 - 14/21
A = 1/21
B = -7/8 × (2/3 - 1)
B = -7/8 × (2/3 - 3/3)
B = -7/8 × (-1/3)
B = 7/8 × 1/3
B = 7/24
C = 4/5 × 1/4 + 2/5
C = 4 × 1/5 × 4 + 2/5
C = 1/5 + 2/5
C = 3/5
J’espère t'avoir t'aider