Pouvez vous m’aider svp merci

Réponse :

A = 3/7 + 4/21 * 5/2

= 3/7 + 10/21         (4/21 * 5/2 = 2/21 * 5= 10/21)

= 9/21 + 10/21       (3/7 = (3*3)/(7*3) = 9/21)

= 19/21

______

B = (3/7 - 4/21) * 5/2

= (9/21 - 4/21) * 5/2

= (5/21) * 5/2

= 25/42

______

C = 2 + 1/3 * 3/5 + 2

= 2 + 2 + 1/5          (1/3 * 3/5 = 1 * 1/5 = 1/5)

= 4 + 1/5

= 20/5 + 1/5

= 21/5

Voilà