12/15 - 2/15 =
100/60
lowest term 17/18 - 2/18 =
6/540
60/100
lowest term 6/9 - 3/9 =
lowest term 18/32 - 12/32 =
lowest term 20/25 - 10/25 =
lowest term 8/40 + 12/40 =
lowest term 4/10 + 2/10 =
