Bonsoir,

a. 2/3 + 8/15 = 6/5

2/3 = (2 x 10) / (3 x 10) = 20/30

8/15 = (8 x 2) / (15 x 2) = 16/30

6/5 = (6 x 6) / (5 x 6) = 36/30

b. 7/2 x 5/14 = 5/4

7/2 x 5/14 = 35/28 = (7 x 5) / (7 x 4) = 5/4

c. 9/8 - 7/16 = 11/16

9/8 = (9 x 2) / (8 x 2) = 18/16

18/16 - 7/16 = 11/16.