18. Consider the following "star" figure.

Given that $\angle p+\angle q+\angle r+\angle s+\angle t=500^{\circ}$ and $\angle A+\angle B+\angle C+\angle D+\angle E=x^{\circ}$, find the value of $x$.
18. Ans: 140 .
Use angle sum of polygons,
$$
x=140 . \quad x^{\circ}+5 \times 360^{\circ}-(\angle p+\angle Q+\angle r+\angle s+\angle t)=8 \times 180^{\circ},
$$