What is addition, subtraction, multiplication and division?

Addition: add a number to a number, column: 90+ 10= 100.

Division: learn to do division first. Column: 6 times 7 equals 42. 42 divided by 7 equals 6(42 divided by 6 equals 7).

Subtraction: There is a very large number followed by a very small number, column: 50-30=20.