Solve the System $\left\{ \begin{array} { l } 9 x - y = 7 \\8 x + 9 y = - 9\end{array} \right.$

Multiple Choice

Solve the system $\left\{ \begin{array} { l } 9 x - y = 7 \\8 x + 9 y = - 9\end{array} \right.$ by Cramer s rule. Write the determinant $D _ { x }$ .

A) $\mid \begin{array} { c c } 9 & - 1 \\8 & 9\end{array}$
B) $\left| \begin{array} { c c } 7 & - 1 \\- 9 & 9\end{array} \right|$
C) $\begin{array} { c c } 9 & 7 \\8 & - 9\end{array}$
D) $\left| \begin{array} { c c } - 7 & - 1 \\9 & 9\end{array} \right|$