The three angles are 42, 73 and 65 degrees. Let's call them x,y, and z respectively x = 42 y = 73 z = 65
To find an exterior angle for x, we subtract the given angle x from 180 180-x = 180-42 = 138 The exterior angle adjacent to angle x is 138 degrees. This isn't listed so we move on
Do the same for y 180-y = 180-73 = 107 This isn't listed either. So we move on
Repeat for angle z 180-z = 180-65 = 115 This is listed as choice C. That's why choice C is the answer
