b = 3/ 4 + 1 / 6
b = 3x 6/ 4 x 6 + 1x 4 / 6 x 4
b = 18/24 +4/24
b = 22/24 = 11/12
c = 5 / 6 - 3 / 10
c = 5x 10 /6x 10 - 3x 6 / 10 x6
c = 50 / 60 - 18 /60
c = 42 / 60 = 7 /10
d = 7 /8 - 11 /20
d = 7 x 20 / 8 x 20 - 11 x 8 / 20 x 8
d = 140 /160 - 88 / 160
d = 52 / 160 = 26 / 80 = 13 /40
