By using symbols (pro-numerals) to represent unknowns, algebra enables us to solve problems by writing information as mathematical sentences or statements. These statements are expressions. Expressions are made up of terms which can be simplified by collecting like terms. The distributive law states that ‘a term outside a bracket in an expression multiplies each term inside the bracket.’ Expressions are evaluated by substituting numbers into expressions in a correct sequence. A formula explains a process for working out a result, when an expression is connected to a symbol by an equals sign (eg. P = 2L + 2W gives the perimeter of a rectangle). Formulae are worked out by substituting values for the variable or pro-numerals.
