jmc

A pentagon can be partitioned into three triangles, so the sum of the degree measures of the angles of the pentagon is $$v+w+x+y+z=540.$$The arithmetic sequence can be expressed as $x-2d$, $x-d$, $x$, $x+d$, and $x+2d$, where $d$ is the common difference, so $$(x-2d)+(x-d)+x+(x+d)+(x+2d)=5x=540.$$Thus, $x=\boxed{108}$.