Salut!
1) A = 1 - [(2/3)+(1/4)] = 1 - [ (2x4 + 1x3)/(3x4)] = 1 - (11/12) = (12-11)/12 = 1/12
B = en haut 3- 5/2 = (6-5)/2 = 1/2
en bas 1 + 1/5 = (5+1)/5 = 6/5
donc B = (1/2)/ (6/5) = (1/2) x (5/6) = (1x5)/(2x6) = 5/12
2) C = (4/5) x (35/8) = (4 x 5 x 7) / (5 x 4 x 2) = 7/2
3) A+B = 1/12 + 5/12 = 6/12 = 1/2
C = 7/2
A+B+C = (1+7)/2 = 8/2 = 4