For equations with multiple steps, operations must be performed in the following order: brackets, indices, division and multiplication, addition and subtraction. An acronym to remember this is BIDMAS. For the operations that rank equally, operations are performed from left to right.

An expression is a set of terms combined using mathematical operations. An equation is a mathematical statement which shows that two expressions are equal. A formula is a rule written in mathematical symbols, which is given as an equation made up of physical quantities. An identity is an equation which is true for any values chosen for the variables.

When writing algebraic equations or expressions, letters are used to represent unknown values, these are known as variables. The rules of algebraic notation given in the table can be used to write and interpret algebraic expressions and equations.

The value of an expression can be calculated by putting known values into it in the place of variables and carrying out the operations using BIDMAS. This replacement of letters into values is called substitution.

for expression A:
5 × 8 − 5² + (6 − 1) =
= 5 × 8 − 5² + 5 =
= 5 × 8 − 25 + 5 =
= 40 − 25 + 5 = 20

for expression B:
6² + (3 × 3) − (20 + 5) =
= 6² + 9 − 25 =
= 36 + 9 − 25 = 20

for expression C:
(9 × 7) ÷ (5 − (2 × 2) + 2) =
= 63 ÷ (5 − 4 + 2) =
= 63 ÷ 3 = 21

Thus, expression C is the one that equates to 21.

C

The expression in algebraic notation is (ab + 4)³.

(ab + 4)³

An expression is a set of terms combined using mathematical operations, whereas an equation is a statement which shows two expressions which are equal.

set of terms versus several expressions

Using BIDMAS, 11 × (4 + 2)² = 11 × 6² = 11 × 36 = 396.

396

An expression is a set of terms combined using mathematical operations.

a set of terms with mathematical operations