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Bonjour

5/7 + (2/7 - 5)

= 5/7 + [2/7 - (5 x 7) / (1 x 7)]

= 5/7 + (2/7 - 35/7)

= 5/7 - 33/7

= 28/7

= (7 x 4) / (7 x 1)

= 4.

7/3 - 4/3 : 2/5

= 7/3 - 4/3 x 5/2

= 7/3 - 20/6

= (7 x 2) / (3x 2) - 20/6

= 14/6- 20/6

= - 6/6

= - 1

4/5x (5/4 + 1) - 3/10

= 4/5 x [5/4 + (1  x 4) / (1 x 4)] - 3/10

= 4/5 x (5/4 + 4/4) - 3/10

= 4/5 x 9/4 - 3/10

= 36/45 - 3/10

= (9 x 4) / (9 x 5) - 3/10

= 4/5 - 3/10

= (4  x 2) / (5 x 2) - 3/10

= 8/10 - 3/10

= 5/10

= (5x 1) / (5x  2)

= 1/2.