Solve the System of Equations by the Addition Method $\left\{ \begin{array} { l } x + y = 0 \\x - y = 14\end{array} \right.$

Multiple Choice

Solve the system of equations by the addition method.
- $\left\{ \begin{array} { l } x + y = 0 \\x - y = 14\end{array} \right.$

A) $( 6 , - 6 )$
B) no solution
C) $( - 7 , - 6 )$
D) $( 7 , - 7 )$