bonjour
1/12
1/12 + 4/3 = 1/12 + 16/12 = 17/12
17/12 - 7/10 = 170/120 - 84/120 = 86/120 = 43/ 60
43/60 - 5/2 = 43/60 - 150/60 = - 107/60
fais pareil avec 2/9
2/5 + 1/7 + 3/14 = 2/5 + 2/14 + 3/14 = 28/70 + 10/70 + 15/70 = 53/70
la pelouse correspond = 17/70