### Home > AC > Chapter 7 > Lesson 7.3.4 > Problem7-113

7-113.

Peggy decided to sell brownies and cookies to raise money for her basketball uniform. She sold brownies for $3.00$ and cookies for $2.50$. If she sold $3$ fewer cookies than brownies and collected $218$ in all, then how many brownies did she sell? Write and solve an equation (or a system of equations) to find your solution.

Write an equation for the problem.

\begin{aligned} x - 3 &= y \\ 3x + 2.5y &= 218 \end{aligned}

$y = \text{the number of cookies}$

Substitute for $y$ in the second equation and solve for $x$, the number of brownies.

\begin{aligned} 3x + 2.5\left(x - 3\right) &= 218 \\ 3x + 2.5x - 7.5 &= 218 \\ 5.5x &= 225.5\\ x &= 41 \end{aligned}