Bonjour
A = 2/5 - 7/15
A = (2 x 3) / (5 x 3) - 7/15
A = 6/15 - 7/15
A = - 1/15
B = 3 + 1/8
B = (3 x 8) / (1 x 8) + 1/8
B = 24/8 + 1/8
B = 25/8
C = - 5/7 x 3/10
C = - 15/70
C = (5 x - 3) / (5 x 14)
C = - 3/14
D = 1/5 + 1/5 (4/12 + 3/9)
D = 1/5 + 1/5 [(4 x 3) / (12 x 3) + (3 x 4) / (9 x 4)]
D = 1/5 + 1/5 (12/36 + 12/36)
D = 1/5 + 1/5 (24/36)
D = 1/5 + 1/5 [(12 x 2) / (12 x 3)]
D = 1/5 + 1/5 (2/3)
D = (1 x 3) / (5 x 3) + 2/15
D = 3/15 + 2/15
D = 5/15
D = (5 x 1) / (5 x 3)
D = 1/3.
