Réponse :
Bonjour
Explications étape par étape
6/12 /7/12 = 6/12 X 12/7 = 72/84 = 24/28 = 12/14 = 6/7
3/2 +7/3 = 3/2 X 3/3 +7/3 X 2/2 = 9/6 +14/6 = 23/6
3/4 -2/3 = 3/4 X 3/3 -2/3 X 4/4 = 9/12 -8/12 = 1/12
-3/7 +5/14 = -3/7 X 2/2 +5/14 = -6/14 + +5/14 = -1/14