Pouvez vous m'aider pour l'exercice 49 merci

Bonjour,

A = 7/3 - 4/3 + 8/5
A = 3/3 + 8/5
A = (3 x 5) / (3 x 5) + (8 x 3) / (5 x 3)
A = 15/15 + 21/15
A = 36/15
A = (3 x 12) / (3 x 5)
A = 12/5

B = - 4/9 x 1/5 + 3/7
B = - 4/45 + 3/7
B = (- 4 x 7) / (45 x 7) + (3 x 45) / (7 x 45)
B = - 28/315 + 135/315
B = 107/315

C = - 8/3 + - 5/6 + 7/4
C = - 8/3 - 5/6 + 7/4
C = (8 x 8) / (3 x 8) - (5 x 4) / (6 x 4) + (7 x 6) / (4 x 6)
C = 64/24 - 20/24 + 42/24
C = 106/24 - 20/24
C = 86/24
C = (2 x 43) / (2 x 12)
C = 43/12