Solve the System by the Substitution Method or the Addition $\left\{ \begin{array} { l } 3 ( 2 x + y ) = 4 x + 21 \\x - 2 y = 0\end{array} \right.$

Multiple Choice

Solve the system by the substitution method or the addition method.
- $\left\{ \begin{array} { l } 3 ( 2 x + y ) = 4 x + 21 \\x - 2 y = 0\end{array} \right.$

A) $( 6,3 )$
B) $( - 3,6 )$
C) $( 4,2 )$
D) no solution