Réponse :
Explications étape par étape
Bsr,
1/2 + 1/3 = 3/6 + 2/6 = 5/6
1/3 +1/4 = 4/12 + 3/12 = 7/12
1/4 + 1/5 = 5/20 + 4/20 = 9/20
1/5 +1/6 = 6/30 + 5/30 = 11/30
5/6 + 7/12 = 10/12 + 7/12 = 17/12
7/12+ 9/20 = 70/120 + 54/120 = 124/120
9/20 + 11/30 = 27/60 + 22/60 = 49/60
17/12 + 124/120 = 170/120 + 124/120 = 294/120
124/120 + 49/60 = 124/120 + 248/120 = 372/120
294/120 + 372/120 = 666/120= 333/ 60 = 111/ 20