8. An angle can be represented by two capital letters on its two sides and the letter of its vertex, such as $\angle A O B$ symbol (" $\angle$ " represents an angle), or it can also be represented by $\angle O$ (when there is only one angle at the vertex). In the triangle $\mathrm{ABC}$ below, $\angle B A O=\angle C A O$, $\angle C B O=\angle A B O, \angle A C O=\angle B C O, \angle A O C=110^{\circ}$, then $\angle C B O=$
【Answer】 $20^{\circ}$