bonjour
A = 1 - 1/3 - 2/20
A = 60/60 - 20/60 - 6/60
A = 34/60 = 17/30
C = 1 - ( 4/12 + 3/12) x 2 /5
C = 1 - 7/12 x 2/5
c = 1 - 14/60
C = 60/60 - 14 /60
C = 46/60 = 23/30
B = tu fais = la même que haut dessus, seul le signe change