Bonjour
A = 8/7 + 5/7 x 1/15
A = 8/7 + 5/105
A = (8 x 15) / (7 x 15) + 5/105
A = 120/105 + 5/105
A = 125/105
A = (5 x 25) / (5 x 21)
A = 25/21.
B = 4/9 - 8/9 : 16/5
B = 4/9 - 8/9 x 5/16
B = 4/9 - 40/144
B = (4 x 16) / (9 x 16) - 40/144
B = 64/144 - 40/144
B = 24/144
B = (24 x 1) / (24 x 6)
B = 1/6
C = (7/4 - 2) : (5/4 + 3)
C = [7/4 - (2 x 4) / (1 x 4)] : [5/4 + (3 x 4) / (1 x 4)]
C = (7/4 - 8/4) : (5/4 + 12/4)
C = - 1/4 : 17/4
C = - 1/4 x 4/17
C = - 4/68
C = (4 x - 1) / (4 x 17)
C = - 1/17
D = (5 - 2/5) : (4/5 + 9)
D = [(5 x 5) / (1 x 5) - 2/5] : [4/5 + (9 x 5) / (1 x 5)]
D = (25/5 - 2/5) : (4/5 + 45/5)
D = 23/5 : 49/5
D = 23/5 x 5/49
D = 115/245
D = (5 x 23) / (5 x 49)
D = 23/49.
