Bonjour,

A = 7/15 + 2/15

A = 9/15

A = (3 x 3) / (3 x 5)

A = 3/5

B = 7/18 + 5/6

B = 7/18 + (5 x 3) / (6 x 3)

B = 7/18 + 15/18

B = 32/18

B = (2 x 16) / (2 x 9)

B = 16/9

C = 3 - 5/6

C = (3 x 6) / (1 x 6) - 5/6

C = 18/6 - 5/6

C = 13/6

D = 3/5 - 5/9

D = (3 x 9) / (5 x 9) - (5 x 5) / (9 x 5)

D = 27/45 - 25/45

D = 2/45

E = 18/27 + - 20/15

E = (9 x 2) / (9 x 3) - (5 x 4) / (3 x 4)

E = 2/3 - 5/3

E = - 3/3

E = - 14

F = 5/3 - 7/4 - 5/12

F = (5 x 4) / (3 x 4) - (7 x 3) / (4 x 3) - 5/12

F = 20/12 - 21/12 - 5/12

F = - 6/12

F = (6 x - 1) / (6 x 2)

F = - 1/2.