How do you learn the four operations of arithentic?
By paying attention in school. You can also review your school textbooks - and read online articles about basic math. - Please note that you basically need to learn how to add, subtract, multiply and divide not just whole numbers, but also numbers with decimals, and fractions.
The Four Fundamental Operations (Addition, Multiplication, Subtraction and Division) form the basis of the whole study of mathematics and numerical science. These operations form all the other operations that we use in the above specified subjects. So they are called Fundamental Operations Because the can't be derived either in the terms of themselves or any other operator.