Bonjour,

40)

a. 7/10 + 1/10 = 8/10 = (2 x 4) / (2 x 5) = 4/5

b. 7/4 - 1/4 = 6/4 = (2 x 3) / (2 x 2) = 3/2

c. 3/7 + 2/7 = 5/7

41)

a. 7/15 + 3/15 = 10/15 = (5 x 2) / (5 x 3) = 2/3

b. 5/8 - 1/8 = 4/8 = (4 x 1) / (4 x 2) = 1/2

c. 7/9 - 1/9 = 8/9.