The letters are often called variables.
It is necessary to be able to add, subtract, multiply and divide algebraic terms.
Addition and Subtraction
An expression involving addition and subtraction can be simplified only if it contains like terms.
The like terms are collected together and then added or subtracted.
3xy means "3 multiplied by x multiplied by y ".
In terms of this type the number comes first and the variables are usually placed in alphabetical order.
e.g. 3q × 4p = 12pq
Note that numbers are multiplied first and letters (variables) are placed in alphabetical order.
Words into Symbols
Many maths problems are written in words and these words often have to be changed into algebraic expressions.