Bonjour pourriez vous m'aidez s'il vous plaît ?

Bonjour,

a) 9/7 + 6/14

= (9 x 2) / (7 x 2) + 6/14

= 18/14 + 6/14

= 24/14

= (2 x 12) / (2 x 7)

= 12/7

b) 9/7 - 18/21

= (9 x 3) / (7 x 3) - 18/21

= 27/21 - 18/21

= 9/21

= (3 x 3) / (3 x 7)

= 3/7

c) 2/5 + 7/20

= (2 x 4) / (5 x 4) + 7/20

= 8/20 + 7/20

= 15/20

= (5 x 3) / (5 x 4)

= 3/4

d) 2/5 - 20/25

= (2 x 5) / (5 x 5) - 20/25

= 10/25 - 20/25

= - 10/25

= (5 x - 2) / (5 x 5)

= - 2/5.