Réponse :
coucou,
a)
3/8 - 2/7 = 5/56
car
2/7 = 16/56
3/8 = 21/56
(21 -16)/56 = 5/56
b)
5/4 * 12/25=3/5
car
5/4 * 12/25 = (5*12)/(4*25) = 60/100
(60 :20)/(100 :20) = 3/5
c)
2 - 1/9=17/9
car
2 = 2/1 = 18/9
1/9 = 1/9
2 - 1/9 = 18/9 - 1/9 = 17/9
d)
9/7 + 2/3=41/21
car
9/7= 27/21
2/3 = 14/21
9/7 + 2/3 = 27/21 +14/21 = 41/21
e)
15/8 : 3/7=35/8
car
15/8 : 3/7 = 15/8 * 7/3 = (15*7)/(8*3) = 105/24
105/24 = (105:3) / (24:3) = 35/8
f)
5 : 3/4=20/3
car
5 = 5/1
3/4 = 3/4
5/1 : 3/4 = 5/1 * 4/3 = (5*4)/(1*3) = 20/3
