Step One Find RST The two base angles are given as equal and one of the is 28. So is the other one. SRT = 28 STR = 28 All triangles have interior angles that add up to 180 degrees.
Step two Find the exterior angle The exterior angle = Sum of the two remote interior angles (RST + SRT) The exterior angle = 28 + 124 The exterior angle = 152
Step Three Find the value of x 2*x = 152 Divide by 2 x = 152 / 2 x = 76
There is a quicker way of finding the exterior angle. I didn't see it until I had written step two. The exterior angle + STR = 180 degrees. They are supplementary. The exterior angle + 28 = 180 The exterior angle = 180 - 28 The exterior angle = 152
