• Like terms have the same variables with the same powers.
• They may have different coefficients.
• The terms 4x and 7x are like terms, but 4x and 4x² are not.
• To simplify an expression, we add the coefficients of like terms only. For example, 3x + 5x = 8x, and 4x² − x² = 3x².

Removing brackets

• If a bracket is preceded by a plus sign, we keep the signs inside it.
• If it is preceded by a minus sign, we change the sign of every term inside it.
• If a number stands in front of the bracket, we multiply every term inside by that number:

1. a − (b − c) = a − b + c
2. 2(3x − 4) = 6x − 8
3. −(2m − n) = −2m + n