Bonjour
11)
a. 1/10 + 7/5 = 1/10 + (7 x 2) / (5 x 2) = 1/10 + 14/10 = 15/10 = (5 x 3) / (5 x 2) = 3/2
b. 3/2 + 13/2 = 16/2 = (2 x 8) / (2 x 1) = 8
c. 27/16 - 7/16 = 20/16 = (4 x 5) / (4 x 4) = 5/4
d. 10/24 + 5/6 = 10/24 + (5 x 4) / (6 x 4) = 10/24 + 20/24 = 30/24 = (6 x 5) / (6 x 4) = 5/4
12)
a. 1/13 + 1/39 = (1 x 3) / (13 x 3) + 1/39) = 1/39 + 3/39 = 4/39
b. 1/13 - 1/39 = 3/39 - 1/39 = 2/39
c. 1/17 + 1/51 = (1 x 3) / (17 x 3) + 1/51 = 3/51 + 1/51 = 4/51
d. 1/17 - 1/51 = 3/51 - 1/51 = 2/51
e. 9/15 + 3/5 = (3 x 3) / (3 x 5) + 3/5 = 3/5 + 3/5 = 6/5
f. 9/15 - 3/5 = 3/5 - 3/5 = 0.
