Use the Gauss-Jordan Method to Solve the System of Equations $$\begin{array} { l } x + y = 3 \\x - y = - 4\end{array}$$

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.
- $$\begin{array} { l } x + y = 3 \\x - y = - 4\end{array}$$

A) $\left\{ \left( - \frac { 1 } { 2 } , - \frac { 1 } { 2 } \right) \right\}$
B) $\left\{ \left( \frac { 7 } { 2 } , - 2 \right) \right\}$
C) $\varnothing$
D) $\left\{ \left( - \frac { 1 } { 2 } , \frac { 7 } { 2 } \right) \right\}$