Je n'y comprends rien il me faudrait la réponse avec 15h merci

bonjour

a = ( 1/2 + 4/3) x 6/5
a = ( 3/6 + 8/6) x 6/5
a = 11/6 x 6/5
a = 66/ 30 = 11/5

b = 15 : ( 1/4 - 2/3)
b = 15 :  3/12 - 8/12
b = 15 : - 5/12
b = 15 x - 12/5
b = -36

c = ( 4/3 + 2) : ( 4/3 + 7/5)
c = ( 4/3 + 6/3) : ( 20/15 + 21/15)
c = 10/3 : 41/15
c = 10/3 x 15/41
c = 150/123 = 50/41

d = (2/3 : 5/6) - 2/5
d = (2/3 x 6/5) - 2/5
d = 12/15 - 2/5
d = 12/15 - 6/15
d = 6/15 = 2/5