Note: Figure not drawn to scale.

In the figure, line $m$ is parallel to line $n$, and line $k$ intersects both lines. The angle labeled $a^{\circ }$ is given by the expression $(3x-10{)}^{\circ }$. The angle above line $m$ and to the left of line $k$ is given by the expression $(x+50{)}^{\circ }$. What is the value of $x$?