5/9+7/8= 5/18++7/18=12/18
13/15*5/8=13/3*1/8=13/24
14/17-5/17=9/17
12/19:3=12/19*1/3=12/57
2/3-1/4=2/12-1/12=1/12
5/8:7/8=5/8*8/7=48/56
