Learn it
A variable is a letter that stands for a number we do not know or that can change. An expression combines numbers, variables and operations, like 3x + 5.
- “5 more than n” → n + 5
- “twice a number” → 2n
- “8 less than y” → y − 8
- “the quotient of m and 4” → m ÷ 4 or m/4
In 3x + 5, 3 is the coefficient, x is the variable and 5 is the constant.
Worked examples
Example 1
Write an expression: 7 less than 4 times a number k.
- 4 times k is 4k
- 7 less than that means subtract 7
Answer: 4k − 7
Example 2
Tickets cost $9 each plus a $3 fee. Write an expression for the cost of t tickets.
- Ticket cost: 9t
- Add the fee
Answer: 9t + 3
Practice
Try these on paper first, then check your work.
- A number d decreased by 12
- The product of 6 and w
- Half of a number p
- 3 more than twice x
Show the answer key
- d − 12
- 6w
- p/2
- 2x + 3