Réponse:
O = 18/8 - 3/4
= 9/4 - 3/4
= 6/4
O = 3/2
P = 12/7 - 27/21
= 12/7 - 9/ 7
= 3/7
S=12/15 + 3/5
= 4/5 + 3 /5
= 7/5
T = 8/42 + 5/7
= 4/21 + 5/7
= 4/21 + 15/ 21
=19 / 21
