Bonsoir
A = 7/10 - 3/4 + 2/5
A = (7 x 6) / (10 x 6) - (3 x 15) / (4 x 15) + (2 x 12) / (5 x 12)
A = 42/60 - 45/60 + 24/60
A = 21/60
A = (3 x 7) / (3 x 20)
A = 7/20
B = (12/5 - 13/10) - (8/3 - 4/9)
B = [(12 x 2) / (5 x 2) - 13/10] - [(8 x 3) / (3 x 3) - 4/9]
B = (24/10 - 13/10) - (24/9 - 4/9)
B = 11/10 - 20/9
B = (11 x 9) / (10 x 9) - (20 x 10) / (9 x 10)
B = 99/90 - 200/90
B = - 101/90
C = 7/3- 4/3 : 8/5
C = 7/3 - 4/3 x 5/8
C = 7/3 - 20/24
C = (7 x 8) / (3 x 8) - 20/24
C = 56/24 - 20/24
C = 36/24
C = (12 x 3) / (12 x 2)
C = 3/2
D = - 7/5 : (2/9 - 7/18)
D = - 7/5 : [(2 x 2) / (9 x 2) - 7/18]
D = - 7/5 : (4/18 - 7/18)
D = - 7/5 : (- 3/18)
D = - 7/5 x (- 18/3)
D = 126/15
D = (3 x - 42) / (3 x 5)
D = - 42/5.
