Bonsoir,
A = 2/7 + 3/5 x 7/3
A = 2/7 + 21/15
A = 2/7 + (3 x 7) / (3 x 5)
A = 2/7 + 7/5
A = (2 x 5) / (7 x 5) + (7 x 7) / (5 x 7)
A = 10/35 + 49/35
A = 59/35
B = (2/7 + 3/5) x 7/3
B = [(2 x 5) / (7 x 5) + (3 x 7) / (5 x 7)] x 7/3
B = (10/35 + 21/35) x 7/3
B = 31/35 x 7/3
B = 217/105
B = (7 x 31) / (7 x 15)
B = 31/15
C = 2/7 x 3/5 x 7/3
C = 6/35 x 7/3
C = 42/105
C = (21 x 2) / (21 x 5)
C = 2/5
D = 2/7 - 3/5 : 7/3
D = 2/7 - 3/5 x 3/7
D = (2 x 5) / (7 x 5) - 9/35
D = 10/35 - 9/35
D = 1/35.