Bonjour quelqu'un pourrait m'aider pour ces exercices s'il vous plaît ? Je n'y arrive pas​

Bonjour,

1)

A = 1 - (1/3 + 1/4) x 2/5

A = 1 - [(1 x 4) / (3 x 4) + (1 x 3) / (4 x 3)] x 2/5

A = 1 - (4/12 + 3/12) x 2/5

A = 1 - 7/12 x 2/5

A = 1 - 14/60

A = (1 x 30) / (1 x 30) - (2 x 7) / (2 x 30)

A = 30/30 - 7/30

A = 23/30

B = 1 - 1/3 - 1/4 x 2/5

B = 1 - 1/3 - 2/20

B = 1 - 1/3 - (2 x 1 / 2 x 10)  

B = 1 - 1/3 - 1/10

B = (1 x 30) / (1 x 30) - (1 x 10) / (3 x 10) - (1 x 3) / (10 x 3)

B = 30/30 - 10/30 - 3/30

B = 30/30 - 13/30

B = 17/30.

C = (1 - 1/3 - 1/4) : 2/5

C = [(1 x 12) / (1 x 12) - (1 x 4) / (3 x 4) - (1 x 3) / (4 x 3)] x 5/2

C = (12/12 - 4/12 - 3/12) x 5/2

C = 5/12 x 5/2

C = 25/24

D = (1 - 1/3 - 1/4) x 2/5

D = 5/12 x 2/5

D = 10/60

D = (10 x 1) / (10 x 6)

D = 1/6.

2) Réponse D = 1/6.