20 point!!!!!! aider moi a faire le 89

Exercice - 89 :

a = 1 / 5 - 8 / 15 x 5 / 4
= 1 / 5 - 40 / 60
= 12 / 60 - 40 / 60
= - 28 / 60
= - 7 / 15

b = ( 1 / 5 - 8 / 15 ) x 5 / 4
= ( 3 / 15 - 8 / 15 ) x 5 / 4
= - 5 / 15 x 5 / 4
= - 25 / 60
= - 5 / 12

c = - 4 / 7 : 5 / 14 + 5 / 6
= - 4 / 7 x 14 / 5 + 5 / 6
= - 56 / 35 + 5 / 6
= - 336 / 210 + 175 / 210
= - 161 / 210
= - 23 / 30

d = - 4 / 7 : ( 5 / 14 + 5 / 6 )
= - 4 / 7 : ( 30 / 84 + 70 / 84 )
= - 4 / 7 : 100 / 84
= - 4 / 7 x 84 / 100
= - 336 / 700
= - 12 / 25