Chapter 6 - Systems of Equations and Inequalities - 6-2 Solving Systems Using Substitution - Apply What You've Learned - Page 377: c

The solution of the system is $(\displaystyle \frac{80}{3},\frac{40}{3})$

Substitute $2y$ for $x$ in the first equation $x+y=40$ $(2y)+y=40$ $3y=40$ $y=\displaystyle \frac{40}{3}$ minutes Substitute back into $x=2y$ $x=2\displaystyle \cdot\frac{40}{3}=\frac{80}{3}$ minutes The solution of the system is $(\displaystyle \frac{80}{3},\frac{40}{3})$