Learning objectives
Use letters to represent unknown numbers and solve simple equations.
By the end of this course, you should be able to explain the key ideas, use the methods and answer practice questions.
Lesson notes
Variables and constants
A variable is a letter representing a number, such as x. A constant is a fixed number, such as 5.
Expressions
An expression combines numbers, variables and operations. For example, 3x + 2.
Substitution
If x = 4, then 3x + 2 = 3 × 4 + 2 = 14.
Simple equations
Solve x + 5 = 12 by subtracting 5 from both sides. Therefore x = 7.
Like terms
Like terms have the same variable part. For example, 2x + 3x = 5x.
Worked example
Solve 2x = 18 by dividing both sides by 2. Therefore x = 9.
Practice quiz
Enter an answer for each question. Then select Check answers. For fractions, use forms such as 1/2.