Consecutive angles in a parallelogram are supplementary so their measures add to 180.

18x + 4 + 27x - 4 = 180

45x = 180

x = 180 ÷ 45

x = 4 so use that to get m < DAB. Opposite angles have the same measure so this will be the same as m < BCD.

Consecutive angles are supplementary in a parallelogram...so,

∠ADC + ∠DAB = 180 = (18x + 4) + (27x - 4) = 45x

x = 4, so ∠DAB = 104º

therefore, ∠BCD = 104º

Opposite angles are congruent !