Réponse :

Explications étape par étape :

exercice 2 :

A = 10x3/7x3 + 14/21

A = 30/21 + 14/21

A = 44/21

B = 4x3/5x3 + 2/15

B = 12/15 + 2/15

B = 14/15

C = 3x4/4x4 + 5/16

C = 12/16 + 5/16

C = 17/16

exercice 3 :

A = 2x4/3x4 + 5/12

A = 8/12 + 5/12

A = 13/12

B = 19/12 - 3x6/2x6

B = 19/12 - 18/12

B = 1/12

C = 3x3/7x3 + 5/21

C = 9/21 + 5/21

C = 14/21

D = 11/9 - 2x3/3x3          E = 15/8 - 5x2/4x2              F = 7x2/5x2 + 11/10

D = 11/9 - 6/9                  E = 15/8 - 10/8                     F = 14/10 + 11/10

D = 5/9                           E = 5/8                                 F = 25/10