Salut !
4/5 = 80/100 = 12/15
21/35 = 3/5 = 42/70
3/5 + 6/5 = 9/5 = 1,8 et 2 - 1,8 = 0,2 = 1/5
1/5 + 3/10 = 2/10 + 3/10 = 5/10 = 1/2
1/8 - 5/6 = 3/24 - 20/24 = -17/24
