Bonjour,
A = 1/4 - 1/4 x 2/3
A = 1/4 - 2/12
A = (1 x 3) / (4 x 3) - 2/12
A = 3/12 - 2/12
A = 1/12
B = (2/3 + 1/2) / (17/9 - 1/3)
B = [(2 x 2) / (3 x 2) + (1 x 3) / (2 x 3)] / [17/9 - (1 x 3) / (3 x 3)]
B = (4/6 + 3/6) / (17/9 - 3/9)
B = 7/6 : 14/9
B = 7/6 x 9/14
B = 63/84
B = (21 x 3) / (21 x 4)
B = 3/4.
