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Bonjour

1)

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

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

A = 12/12 - (8/12 + 3/12)

A = 12/12 - 11/12

A = 1/12

B = (3 - 5/2) : (1 + 1/5)

B = [(3 x 2) / (1 x 2) - 5/2] : [(1 x 5) / (1 x 5) + 1/5]

B = (6/2 - 5/2) : (5/5 + 1/5)

B = 1/2 : 6/5

B = 1/2 x 5/6

B = 5/12

2)

C = 4/5 x 35/8

C = 140/40

C = (20 x 7) / (20 x 2)

C = 7/2

3)

A + B + C

= 1/12 + 5/12 + 7/2

= 1/12 + 5/12 + (7 x 6) / (2 x 6)

= 1/12 + 5/12 + 42/12

= 48/12

= 4.