1)
x=3/4 - 7/12
x=9/12 - 7/12
x = 2/12
x = 1/6
2)
x = 1/9 + 1/6
x = 2/18 + 3/18
x = 5/18
3)
x = 3/8 + 3/5
x = 15/40 + 24/40
x = 39/40
4)
x = 7/12 - 5/24
x = 14/24 - 5/24
x = 9/24
5)
y=1/3 - 2/7
y = 7/21 - 6/21
y= 1/21
6)
x = 7/9+1/6
x = 14/18 + 3/18
x = 17/18
7)
y = 5/32 + 3/8
y = 5/32 + 12/32
y = 17/32
8)
y = 1/2 - 2/5
y = 5/10 - 4/10
y = 1/10