Solve the System by the Substitution Method $$\left\{ \begin{array} { l } 2 x + y = 10 \\2 x + y = 18\end{array} \right.$$

Multiple Choice

Solve the system by the substitution method.
- $$\left\{ \begin{array} { l } 2 x + y = 10 \\2 x + y = 18\end{array} \right.$$

A) $\{ ( 2,8 ) \}$
B) $\{ ( x , y ) \mid 2 x + y = 10 \}$
C) $\{ ( 4,6 ) \}$
D) $\varnothing$