One angle of atriangle measures 12 degrees. the second angle's measurements is five times the third. what is the measure of the third angle

28 degrees. This is because the first angle is 12 degrees, the third is x degrees and the second is 5x. You know that in a triangle the angles add up to 180 degrees so 12 + 5x + x = 180. Then you get 6x = 168 and x = 28 degrees. (**x being the thrid angle**)