Solve the System by the Addition Method $$\begin{aligned}x - 4 y & = - 15 \\8 x - 5 y & = 42\end{aligned}$$

Multiple Choice

Solve the system by the addition method.
- $$\begin{aligned}x - 4 y & = - 15 \\8 x - 5 y & = 42\end{aligned}$$

A) $\{ ( 9,6 ) \}$
B) $\{ ( - 9,7 ) \}$
C) $\{ ( 8,7 ) \}$
D) $\varnothing$