Chapter 6 - Systems of Equations and Inequalities - 6-4 Applications of Linear Systems - Practice and Problem-Solving Exercises - Page 392: 29

Answer C

This year, 6 students joined the class. Then x + 6 = This year students Let I = Students who play an instrument By the given statements, we have the system: $\frac{1}{4}x=I$ $\frac{1}{3}(x+6)-4=I$ Using substitution to solve the system: $\frac{1}{4}x=\frac{1}{3}(x+6)-4$ $\frac{1}{4}x=\frac{1}{3}x+2-4$ $\frac{1}{12}x=2$ $x=24$ Thus: $x+6=24+6=30$