Answer:
Sean is incorrect.
Step-by-step explanation:
The interior angle of this triangle with the exterior angle of 80° is 100°, so the sum of the remaining angles should be 80°, which means (X + 5) + (X - 5) = 80. Take off the parenthesis, 2X = 80, which means X = 40°. This is where Sean's answer was wrong, he forgot that the remaining angles are X + 5 and X - 5 instead of X, which means that the angles in this triangle should actually be 100°, 45°, and 35°.
