Considering angle BAD is 60 degrees, that makes angle BCD also 60 degrees. Since parallelograms have 360 degrees in total, we're still missing 240 degrees. Since angles BAD and BCD are congruent (equal), that means that angles ABC and ADC also have to be congruent. To find their angles, we do 240 divided by 2, which equals 120. Now that we know all of the angles, lets focus on angle ADC. Since angle 1 has been given to us, all we need to do is subtract 78 from 120 which turns out to be 42 degrees, which is the answer.
