Rules in addition and subtraction of algebraic expression?

Addition:

1. look for like terms, combine like terms by adding their numerical coefficient. In adding the numerical coefficient, you have to consider the rules in adding integers.

a. to add two numbers having like signs, add their absolute values and prefix their common sign, then bring down the literal coefficient.

b. to add two numbers having unlike signs, find the difference of their absolute values and prefix to the difference sign of the number having a greater absolute value, then bring down the literal coefficient.

Subtraction:

1. multiply the subtrahend by -1 and proceed to adding algebraic expression.