Solve the system of equations at right.  

$\left. \begin{array} { l } { \frac { 1 } { x } + \frac { 1 } { y } = \frac { 1 } { 2 } } \\ { \frac { 1 } { x } - \frac { 1 } { y } = \frac { 1 } { 6 } } \end{array} \right.$