To formulate a system of equations for this problem, we can define two variables:
- Let \( r \) be the number of sheets of red paper.
- Let \( g \) be the number of sheets of green paper.
From the information provided, we can set up the following equations based on the total number of sheets of paper and the total cost:
-
The total number of sheets of paper: \[ r + g = 19 \]
-
The total cost of the paper: \[ 0.25r + 0.30g = 5.10 \]
So the system of equations is:
\[ \begin{align*}
- & \quad r + g = 19 \
- & \quad 0.25r + 0.30g = 5.10 \end{align*} \]
This system can now be solved to find the number of sheets of red paper \( r \) that Nathan bought.