Bonjour

A = - 2/5 + 7/10

A = (- 2 x 2) / (5 x 2) + 7/10

A = - 4/10 + 7/10

A = 3/10

B = - 2/5 - 7/10

B = (2 x - 2) / (2 x 5) - 7/10

B = - 4/10 - 7/10

B = - 11/10

C = - 2/5 x 7/10

C = - 14/50

C = (2 x - 7) / (2 x 25)

C = - 7/25

D = - 2/5 : 7/10

D = - 2/5 x 10/7

D = - 20/35

E = 4/3 + 7/4

E = (4 x 4) / (3 x 4) + (7 x 3) / (4 x 3)

E = 16/12 + 21/12

E = 37/12

F = 4/3 - 7/4

D = 16/12 - 21/12

D = - 5/12

G = 4/3 x 7/4

G = 28/12

G = (4 x 7) / (4 x 3)

G = 7/3

H = 4/3 : 7/4

H = 4/3 x 4/7

H = 16/21

I = - 3/5 - 7/3 x 4/5

I = - 3/5 - 28/15

I = (- 3 x 3) / (5 x 3) - 28/15

I = - 9/15 - 28/15

I = - 37/15

J = - 2/7 : 5/9 - 8/5 x 7/2

J = - 2/7 x 9/5 - 56/10

J = - 18/35 - 56/10

J = (- 18 x 2) / (35 x 2) - (56 x 7) / (10 x 7)

J = - 36/70 - 392/70

J = - 428/70

J = (2 x - 214) / (2 x 35)

J = - 214/35.