merci de m'aider exercice en pj sur les fractions 4ème

bonjour

a = - 8/12 + 21/12 = 13/12

b  ) - 15/18 - 1/18 = - 16/18 = - 8/9

c)  = - 12/45 = - 4/15

d) = - 7/3 x 5/6 = - 35/18

e = 48/24 + 28/24 - 7/24 + 3/24 = 72/24= 2

f = 7/8 - 33/24 + 7/6 x - 1/4
f = 21/24 - 33 /24  - 7/24
f = - 19/24

g = ( 3/3 + 2/3) : ( 12/15 - 7/15)
g = 5/3 : 5/15
g = 5/3  x 15/5
g = 75/15 = 5