Bonjour,
a) - 3/11 + 1/2
= (- 3 x 2 / 11 x 2) + (1 x 11 / 2 x 11)
= - 6/22 + 11/22
= - 5/22
b) - 5/7 - 2/3
= (- 5 x 3 / 7 x 3) - (2 x 7 / 3 x 7)
= - 15/21 - 14/21
= - 29/21
c) - - 3/4 + - 1/5
= 3/4 - 1/5
= (3 x 5 / 4 x 5) - (1 x 4 / 5 x 4)
= 15/20 - 4/20
= 11/20
d) 5 - 14/24
= (5 x 24 / 1 x 24) - 14/24
= 120/24 - 14/24
= 106/24
= 2 x 53 / 2 x 12
= 53/12