Répondre :
a = 2/7-15 / 7 x 5 / 4
a = 2/7 - 75/28
a = 8/28 - 75/28
a = - 67/28
A= 2/7-15/7x5/4
= 2/7 - 75/28
= 2x4/7x4 - 75/28
= 8/28-75/28
= -67/28
= 2/7 - 75/28
= 2x4/7x4 - 75/28
= 8/28-75/28
= -67/28