Tous les exercice merci de m'avouer répondre

1- A= 1sur2 + 3sur2 x 7sur3
    A= 1sur2 + 3x7sur2x3
    A= 1sur2 + 21sur6
    A= 3sur6 + 21sur6
    A= 24sur6

bonsoir

a = 1/2 + 3/2 x 7/3
a = 1/2 + 21/6
a = 3/6 + 21/6 = 24/6 = 4

b = ( 1/2 + 3/2) x 7/3 
b = 4/2 x 7/3
b = 28/6 = 14/3

c = 20/9 - 5/3 x 2/3
c = 20/9 - 10/9
c = 10/9

d = ( 20/9 - 5/3)  x 20/9 - 5/3 x 2/3
d = (20/9 - 15/9) x 20/9 - 10/9
d = 5/9 x 20/9 - 10/ 9
d = 100/9 - 10/9
d = 90/9 = 10

il a lu 4/7 lundi, il reste 3/7
il a lu mardi : 3/7 x 2/3 = 6/21
3/7 + 6/21 = 9/21 + 6/21 = 15/21
reste  à lire : 6/21 ou 2/7