Pouvez vous m’aidez pour la c et d svp

Bonjour,

C = 2/5 : 7/8 + 10/21
C = 2/5 x 8/7 + 10/21
C = 16/35 + 10/21
C = (16 x 3) / (35 x 3) + (10 x 5) / (21 x 5)
C = 48/105 + 50/105
C = 98/105
C = (7 x 14) / (7 x 15)
C = 14/15

D = (7 + 1/3) x (3 - 1/2)
D = [(7 x 3) / (1 x 3) + 1/3] x [(3 x 2) / (1 x 2) - 1/2)]
D = (21/3 + 1/3) x (6/2 - 1/2)
D = 20/3 x 5/2
D = 100/6
D = (2 x 50) / (2 x 3)
D = 50/3