bonjour,

A =  - 1/2 -  ( - 7/3 )

A  = - 1/2 + 7/3

A =   - 3/6 + 14/6

A =  11 /6

B  = 2/5 : 5/7

B  = 2/5 * 7/5

B = 14/35

C  = 21/66 * 55*35

C  =  1155/2310

C   = 1 /2

D  =  - 7/16 + 5/12 * 3

D = 7/16 + 15/12

D =  21/48 + 60/48

D  = 81 /48

D = 27/16

E =  4/7 - 1/7 :  ( 2 + 5/2)

E = 4/7 - 1 /7 : ( 4/2 + 5/2)

E = 4 /7 - 1 /7 : 7/2

E = 4/7 - 1/7 * 2/7

E = 4/7 - 2/49

E = 28/49 - 2 /49

E = 26/49