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

7-113.

Write an equation for the problem.

*x* − 3 = *y*

3*x* + 2.5*y* = 218

*x* = the number of brownies*y* = the number of cookies.

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

3*x* + 2.5(*x* − 3) = 218

3*x* + 2.5*x* − 7.5 = 218

5.5*x* = 225.5*x* = 41