Bonjour,
A = 5/6 + 2/3
A = 5/6 + (2 x 2) / (3 x 2)
A = 5/6 + 4/6
A = 9/6
A = (3 x 3) / (3 x 2)
A = 3/2
B = 3/4 + - 3/16
B = (3 x 4) / (4 x 4) - 3/16
B = 12/16 - 3/16
B = 9/16
C = 8/35 + - 4/5
C = 8/35 - (4 x 7) / (5 x 7)
C = 8/35 - 28/35
C = - 20/35
C = (5 x - 4) / (7 x 5)
C = - 4/5.