Réponse :
bonjour
A = 5/4 + 7/6
= 15/12 + 14/12
= 29/12
B = - 12/35 x - 14/21
= 168/ 735 = 8/ 35
C = 15/14 : 20/21
= 15/14 x 21/20
= 315 /280
= 9/8
D = 4/7 - 2/7 : 2/3
= 4/7 - 2/7 x 3 /2
= 4/7 - 6/14
= 8/14 - 6 /14 = 2 /14 = 1 /7
Explications étape par étape :