Question

What is the measure of ∠R?

Answer 1

180-(76+68)= 180-144= 36°

Answer 2

The sum of the angles in the triangle always equal 180°.

Therefore:

$m\angle SRT+76^o+68^o=180^o\\\\m\angle SRT+144^o=180^o\ \ \ |-144^o\\\\m\angle SRT=36^o$