Chapter 8 - Systems of Linear Equations and Problem Solving - 8.4 Systems of Equations in Three Variables - 8.4 Exercise Set - Page 538: 25

$$t=0.1666667,\:s=0.3333333,\:r=0.5$$

Solving the system of equations using substitution, we find: $$2-\frac{3}{2}\left(-\frac{18t-7}{12}\right)-6t-\frac{18t-7}{12}+t=1 \\ t=\frac{1}{6}\\ s=-\frac{18\cdot \frac{1}{6}-7}{12}=\frac{1}{3} \\ r=2-\frac{3}{2}\cdot \frac{1}{3}-6\cdot \frac{1}{6}=.5 $$