Use the Gauss-Jordan Method to Solve the System of Equations $\begin{array} { l } 2 x + 5 y = - 7 \\- 6 x - 15 y = 21\end{array}$

Multiple Choice

Use the Gauss-Jordan method to solve the system of equations. If the system has infinitely many solutions, give the
solution with y arbitrary.
$\begin{array} { l } 2 x + 5 y = - 7 \\- 6 x - 15 y = 21\end{array}$

A) $\{ ( - 1 , - 1 ) \}$
B) $\phi$
C) $\left\{ \left( - \frac { 5 } { 2 } y - \frac { 7 } { 2 } , y \right\} \right\}$
D) $\left\{ \left( - \frac { 5 } { 2 } y + \frac { 7 } { 2 } , y \right) \right\}$