Mathmatics
作者：Cristovão Zhu
1. Multiplication
1.1. Multiply by the number
1.1.1. 10*10=100
1.1.2. 11*10=110
2. Addition
2.1. Add more
2.1.1. Examples
2.1.1.1. 1+20=21
2.1.1.2. 40+60=100
3. Division
3.1. Divide by the number
3.1.1. Examples
3.1.1.1. 2/10=10
3.1.1.2. 10/100=10
4. Subtraction
4.1. Take more
4.1.1. Examples
4.1.1.1. 1-10=-9
4.1.1.2. 10-1=9