Algebra and Variables
Algebra uses letters (variables) to represent unknown numbers, allowing us to write general rules and solve problems.
What You Need to Know
Key Concept Diagram
A variable is a letter (like x or n) that stands for a number we do not yet know
An algebraic expression combines numbers, variables, and operations (e.g. 3n + 2)
To evaluate an expression, substitute a value for the variable (e.g. if n = 4, then 3n + 2 = 14)
Simple equations can be solved by working backwards using inverse operations
Key Vocabulary
Variable
A letter used to represent an unknown or changing number in algebra
Expression
A mathematical phrase with numbers and/or variables (e.g. 4x − 1)
Equation
A mathematical statement that two expressions are equal (e.g. 2x + 3 = 11)
Substitute
To replace a variable with a known number to find the value of an expression
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
If n = 5, what is the value of 4n − 3?
Question 2
Solve: x + 7 = 15. What is x?
Question 3
A bag has n apples. After adding 4 more, there are 12. Which equation represents this?
Key Concepts Summary
- ●A variable is a letter (like x or n) that stands for a number we do not yet know
- ●An algebraic expression combines numbers, variables, and operations (e.g. 3n + 2)
- ●To evaluate an expression, substitute a value for the variable (e.g. if n = 4, then 3n + 2 = 14)
- ●Simple equations can be solved by working backwards using inverse operations