Aidez moi je comprend rien au fraction Merci d'avance

Bonsoir,

F = 9/8 + 5/- 12
F = 9/8 - 5/12
F = 9 x 3 / 8 x 3 - 5 x 2 / 12 x 2
F = 27/24 - 10/24
F = 17/24

G = 7/ - 9 + - 2/15
G = - 7/9 - 2/15
G = - 7 x 5 / 9 x 5 - 2 x 3 / 15 x 3
G = - 35/45 - 6/45
G = - 41/45

H = 14/- 10 - - 10/ - 14
H = -14/10 - 10/14
H = - 14 x 14 / 10 x 14 - 10 x 10 / 14 x 10
H = - 196/140 - 100/140
H = - 296/140
H = 4 x - 74 / 4 x 35
H = - 74/35

I = - - 6/- 8 - - 8/ - 6
I = - 6/8 - 8/6
I = - 6 x 3 / 8 x 3 - 8 x 4 / 6 x 4
I = - 18/24 - 24/24
I = - 42/24
I = 6 x - 7 / 6 x 4
I = - 7/4

J = - 21/ - 16 - 25/ - 24
J = 21/16 + 25/24
J = 21 x 3 / 16 x 3 + 25 x 2 / 24 x 2
J = 63/48 + 50/48
J = 113/48