Bonjour
H: 2/3 - 12/21 x 7/8.
H = 2/3 - 84/168
H = 2/3 - (84 x 1) / (84 x 2)
H = 2/3 - 1/2
H = (2 x 2) / (3 x 2) - (1 x 3) / (2 x 3)
H = 4/6 - 3/6
H = 1/6
I = 1- 3/4 x 2/9
I = 1 - 6/36
I = (1 x 6) / (1 x 6) - (6 x 1) / (6 x 6)
I = 6/6 - 1/6
I = 5/6
J= 10/3 - 2/7 x 35/6
J = 10/3 - 70/42
J = 10/3 - (14 x 5) / (14 x 3)
J = 10/3 - 5/3
J = 5/3.