SOLUTION: How do u solve the question A triangle has an exterior angle with a measure of 120°. Can you determine the measures of the interior angles? Explain

Yes, we can determine the sum of two interior angles of the triangle, that are not supplemental to the given exterior angle.

This sum is equal 120°.

It is based on this Theorem (see the lesson Sum of the interior angles of a triangle in this site): 


    An exterior angle of a triangle is equal (is congruent) to the sum of the two angles 
    of the triangle that are not supplemental to the given angle.


Again, we can determine the sum of measures of two interior angles of the triangle, that are not supplemental to the given exterior angle.

But we can not determine the measures of each of these two angles separately/individually.