This is math, not art, just saying. Although, it kinda looks like abstract art at this point.
In problem 13, (10x-17) and (8x+1) are alternate exterior angles. They are both on the outside of the lines and on opposite sides. Alternate exterior angles are congruent which means they equal each other. So, you can set the two equations equal to each other, solve for x, the plug that value back in to the separate equations of each angle.
In this same problem, the bottom two angles form a 180 degree angle or straight line, so if you add both equations together they equal 180, and you can solve for y.
