Two of the angles are given as 55° and 65°.  We can find the third
angle by adding them and subtracting from 180°.

55°+65°=120°, 180°-120°=60°, so the third angle is 60°



Now we find the three exterior angles, by subtracting each interior
angle from 180°:

180°-55°=125°,  180°-65°=115°,  180°-60°=120°




So the ONLY possible values for the exterior angles are 125°, 115°, 120°.

Any value other than 125°, 115°, 120° could not be the measure of an
exterior angle.

Edwin