Bonjour
x = 1 - 1/2 - 2/3 + 3/4
x = (1 x 12) / (1 x 12) - (1 x 6) / (2 x 6) - (2 x 4) / (3 x 4) + (3 x 3) / (4 x 3)
x = 12/12 - 6/12 - 8/12 + 9/12
x = 21/12 - 14/12
x = 7/12
y = 7 x 1/2 - 2/3 x 5/4 + 14/3 x 18/7
y = 7/14 - 10/12 + 252/21
y = 7/14 - 10/12 + (21 x 12) / (21 x 1)
y = (7 x 6) / (14 x 6) - (10 x 7) / (12 x 7) + 12
y = 42/84 - 70/84 + (12 x 84) / (1 x 84)
y = - 28/84 + 1008/84
y = 980/84
y = (28 x 35) / (28 x 3)
y = 35/3.
z = (1 - 1/4) : (2/3 + 2/5)
z = [(1 x 4) / (1 x 4) - 1/4] : [(2 x 5) / (3 x 5) + (2 x 3) / (5 x 3)]
z = (4/4 - 1/4) : (10/15 + 6/15)
z = 3/4 : 16/15
z = 3/4 x 15/16
z = 45/64.
