We see the 3 step method. In this case, we're NOT going to go all the way to a 360, because this is NOT a rectangle neither a square. So, we only go 180. Anyways, 360 by 2 = 180. it's almost the same concept.
So, like we said, the 3 step method. Plug in RTS and simplify by 180. Then, we brake it down from there.
We know that RST is an equilateral(all 3 sides the same length) triangle, and is therefore equiangular(all 3 angles the same value). Therefore, angle S and is equal to one-third of the triangle's angle measure.
