Bonjour
a. 18/28 = (2x 9) / (2 x 14) = 9/14
b. 6/52 = (2 x 3) / (2 x 26) = 3/26
c. 108/38 = (2 x 54) / (2 x 19) = 54/19
d. 118/34 = (2 x 59) / (2 x 17) = 59/17.