Please follow along with these directions on the attached picture so that this makes sense. I have labeled the picture with the variables I used and the angles I figured out.
Let's start in the top left corner. Remember: triangles always have 180°, and straight lines always have 180°.
<h3><em>9x+1=10x-5</em></h3><h3><em>9x=10x-5-1</em></h3><h3><em>9x=10x-4</em></h3><h3><em>10x-4=9x</em></h3><h3><em>10x-9x=4</em></h3><h3><em>x=4</em></h3><h3><em>hope it helps...</em></h3>