If the measures of two angles of a triangle are 99° and 24°, what is the measure of the third angle?

The interior angles of a triangle will add up to 180 degreesalways

99 + 24 + x = 180
123 + x = 180
x = 180 - 123
x = 57 <== ur other angle

The measure of the third angle would be 57°.

All three angles of any triangle add up to 180°, so you would add 99 and 24 to get 123 and subtract 123 from 180 to get 57.