Bonjour,
A = (3/5 - 1/4) : (1 + 4/10)
A = [(3 x 4) / (5 x 4) - (1 x 5) / (4 x 5)] : [(1 x 10) / (1 x 10) + 4/10]
A = (12/20 - 5/20) : (10/10 + 4/10)
A = 7/20 : 14/10
A = 7/20 x 10/14
A = 70/280
A = (70 x 1) / (70 x 4)
A = 1/4
B = (3 + 1/9) : (1/2 - 2/3)
B = [(3 x 9) / (1 x 9) + 1/9] : [(1 x 3) / (2 x 3) - (2 x 2) / (3 x 2)]
B = (27/9 + 1/9) : (3/6 - 4/6)
B = 28/9 : - 1/6
B = 28/9 x - 6
B = - 168/9
B = (3 x - 56) / (3 x 3)
B = - 56/3
C = (3 + 5/4) : (5 - 1/7)
C = [(3 x 4) / (1 x 4) + 5/4] : [(5 x 7) / (1 x 7) - 1/7]
C = (12/4 + 5/4) : (35/7 - 1/7)
C = 17/4 : 34/7
C = 17/4 x 7/34
C = 119/136
C = (17 x 7) / (17 x 8)
C = 7/8.
