Final answer:
The measure of one of the two congruent angles of triangle MNO is 45.7°.
Step-by-step explanation:
An isosceles triangle is a triangle that has two congruent sides and two congruent angles. In this case, triangle MNO is an isosceles triangle with an angle measuring 88.6°.
Since an isosceles triangle has two congruent angles, we can find the measure of the other congruent angle by subtracting the given angle from 180° and dividing the result by 2. So, the measure of one of the other congruent angles is ((180° - 88.6°) / 2) = 45.7°.