1/10+2/5=1/10+4/10=5/10=1/2
1/3-1/2=2/6-3/6=-1/6
1/5+1/4=5/20+4/20=9/20
1/2-1/7=7/14-2/14=5/14
5/8-1/4=5/8-2/8=3/8
1/5-1/2=2/10-5/10=-3/10
1/10+2/5=1/10+4/10=5/10=1/2
1/3-1/2=2/6-3/6=-1/6
1/5+1/4=5/20+4/20=9/20
1/2-1/7=7/14-2/14=5/14
5/8-1/4=5/8-2/8=3/8
1/5-1/2=2/10-5/10=-3/10