How do you do this and what is the answer

All the opposite angles are equal in a parallelogram:

so AB=DB shows it is an isosceles triangle:

so the two angles on the sides are congruent,

let x to be one of the angles:

2x+28=180

2x=152

x=76=∠A

∠A is opposite of ∠DCB so ∠DCB is 76° because of the parallelogram properties

Google it that might work