By the definition of supplementary, angle 1 equals 180 - 65 which is 115. That means by the definitiion of alternate exterior angles that 10x + 5 is also equal to 115 (it is vertical with angle 1 so they are congruent). We can solve for x now. 10x + 5 = 115 and x = 11. Now that we know x we can use it in 4x - 7 to find the measure of that angle. 4(11) - 7 = 37. Now we have 2 angles in the triangle that are 115 and 37. 180 - 115 - 37 = 28, which is the measure of angle 2.
