14-6=14-4
15-9=15-5
11-8=11-1
12-8=10-8
13-7=10-7
16-8=10-8

14-6=(14-4)-2=10-2=815-9=(15-5)-4=10-4=611-8=(11-1)-7=10-7=312-8=2+(10-8)=2+2=413-7=3+(10-7)=3+3=616-8=6+(10-8)=6+2=8