[tex]m\angle AEB+4x=180^o\to m\angle AEB=180^o-4x\\\\\angle DEB=2x+\angle AEB\ \text{and}\ \angle EBC=6x\ \text{are Alternate Interior Angles}\\\\\text{Alternate Interior Angles are congruent (have the same measure)}\\\\\text{Therefore we have the equation:}\\\\m\angle DEB=m\angle EBC\\\\2x+(180^o-4x)=6x\\\\2x+180^o-4x=6x\\\\(2x-4x)+180^o=6x\\\\-2x+180^o=6x\qquad|\text{add 2x to both sides}\\\\180^o=8x\qquad|\text{divide both sides by 8}\\\\22.5^o=x\to x=22.5^o[/tex]
