According to the knowledge system, it can be divided into direct addition and direct subtraction, and carry addition and abdication subtraction.

Direct addition and direct subtraction:

2+ 1 1= 13 9-2=7 7+2=9 1+6=7 10+ 1= 1 1 10+3= 13 8- 1=7

Carry plus abdication minus:

12-3=9 8+3= 1 1 15-8=7 16-5= 1 1 8+5= 13 18-5= 13 6+7= 13 17-6= 1 1