Question 855787
The measures of the {{{n}}} exterior angles, each measuring {{{20^o}}} , add up to {{{360^o}}} , so
{{{n*20^o=360^o}}}-->{{{n=360^o/20^o}}}-->{{{n=18}}} .
THe polygon has {{{18}}} exterior angles, {{{18}}} sides, {{{18}}} vertices, {{{18}}} interior angles.
Each interior angle is supplementary to the adjacent exterior angle,
so each  interior angle measure {{{180^o-20^o=160^o}}} .
The sum of the measures of the {{{18}}} interior angles, each measuring {{{160^o}}} is
{{{18*160^o=highlight(2880^o)}}} .