20. Find the value of x.

The angle supplementary to 160° is $$180 - 160 = 20^{\circ}$$. The angle supplementary to 125° is $$180-125=55^{\circ}$$. The angle supplementary to 55° is $$180 - 55 = 125^{\circ}$$. So, the sum of interior angles in quadrilateral is 360, then $$20+x+125+55 = 360$$, so $$x+200 = 360$$, therefore $$x = 360-200 = 160^{\circ}$$. **Answer: 160°**