so hmm check the picture below
so.. that means the interior angle at the vertex R is 180 - 82, or 98
now, the sum of all interior angles of a polygon is 180(n - 2)
where "n" is how many sides are there in the polygon
this is a pentagon, so 5 sides, so, the sum of all the interior angles is then
180( 5 - 2)
180(3)
540
that means that
98 + 82 + c + 116 + c = 540
2c + 98 + 82 + 116 = 540 <----- solve for "c"
