Two lines intersect, and you know the measure of one angle. How can you determine the measures of the other three angles

Opposite angles are the same measure.

Angles around a point = 360°

When you add all the angles, you get 360.

Angle a and b would measure the same and so would angle d and c. So you double the measure for one of those angles and subtract it from 360.

Then, you half that value( divide by 2) and this is to find the measure of the other angle