Solve the System by the Addition Method $$\begin{array} { l } - 3 x - 4 y = - 21 \\6 x + 8 y = 42\end{array}$$

Multiple Choice

Solve the system by the addition method. $$\begin{array} { l } - 3 x - 4 y = - 21 \\6 x + 8 y = 42\end{array}$$

A) $( - 1,6 )$
B) $( 2 , - 12 )$
C) Infinitely many solutions; $\left\{ ( x , y ) \mid y = - \frac { 3 } { 4 } x + \frac { 21 } { 4 } \right\}$ ; dependent system
D) No solution; { } ; inconsistent system