bjr j'ai besoin d'aide svp

Bonjour,

A = 3/4 : 7/4
A = 3/4 x 4/7
A = 12/28
A = (4 x 3) / (4 x 7)
A = 3/7

B = 25/100 : 2
B = 25/100 x 1/2
B = 25/200
B = (25 x 1) / (25 x 8)
B = 1/8

C = 5 : 4/3
C = 5 x 3/4
C = 15/4