Example 6: Two unknowns
Last Updated On: Fri Aug 28 2026| Order | Pens | Notebooks | Total cost ($) |
|---|---|---|---|
| 1 | 3 | 2 | 19 |
| 2 | 5 | 4 | 35 |
| Unit price ($) | ? | ? | - |
A "?" marks a missing value.
Question
What is the price of one pen and of one notebook?
Solution
- Let a pen cost p and a notebook cost n. Then 3p + 2n = 19 and 5p + 4n = 35.
- Multiply the first equation by 2: 6p + 4n = 38.
- Subtract the second equation: (6p + 4n) - (5p + 4n) = 38 - 35, so p = 3.
- Substitute: 3(3) + 2n = 19, so n = 5.
- A pen costs $3 and a notebook costs $5.