qui peut m'aider c'est urgent svp

a = 12/5 -3/5x7/9 = 12/5 -21/45= 12/5-7/15 = 36/15-7/15 = 29/15

b = 2/3-3  : 1/9 = 2/3-9/3 : 1/3 = -7/3 x9 = -63/3 = -21

c = (2/3-3/2) : 7/11 = (4/6-9/6) :7/11 =-5/6:7/11 =5/6x11/7 =55/42

d = 1/3 +5/6+3/2= 2/6+5/6+9/6 = 16/6 =8/3

e = 2 -5/2 : 15/4 = 2 - 5/2 x4/15 = 2 -20/30 = 2-2/3 = 6/3-2/3 = 4/3

f = (15/8 -1/4 ) : (3/4+15/2) = (15/8 -2/8) : (3/4 +30/4) =(13/8) : (33/4) = 13/8 x4/33 =13/2 x 1/33 = 13/33

2/
said : 1/4
donc il reste  1-1/4 = 4/4 -1/4 = 3/4

sa sœur 2/3 de ce qui reste : 3/4 x2/3 = 6/12 = 1/2
donc il reste
1 -1/4 -1/2 = 4/4 -1/4 -2/4 = 4/4 -3/4 = 1/4

on sait que 1/4 =5
donc
5 : 1/4 = 5x4 =20
il y avait donc 20 gâteaux dans le paquet