Pourriez vous m'aider pour les calculs merci

Bonjour,

A = 7/2 - 3/4
A = 7 x 2 / 2 x 2 - 3/4
A = 14/4 - 3/4
A = 11/4

B = 4/7 + 2
B = 4/7 + 2 x 7 / 1 x 7
B = 4/7 + 14/7
B = 18/7

C = 11/4 : 7/18
C = 11/4 x 18/7
C = 198/28
C = 2 x 99 / 2 x 14
C = 99/14

D = 24/36 x 9/27
D = 216/972
D = 108 x 2 / 108 x 9
D = 2/9