Quadrilateral $abcd$ is a parallelogram. if the measure of angle $a$ is 62 degrees and the measure of angle $adb$ is 75 degrees, what is the measure of angle $adc$, in degrees?

To better illustrate the problem, the first step is to draw the figure like what is shown in the picture. By definition, a parallelogram is a quadrilateral, such that it has two sets of parallel lines. The adjacent angles are not equal but they are supplementary. Meaning, when you add 60° and angle ADC, the sum would be 180°.

Therefore,

Angle ADC = 180°-60° = 120°

We could actually do without the additional detail pertaining to 75°. However, we could find angle CDB by difference. The solution would be 120°-75° = 45°. But this is not anymore needed by the problem because it is not asked. I guess the 75° is just a distraction.