In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data
Quadrilateral ABCD
∠ D = ?
∠ A = 54
∠ B = 110
Step 02:
We must apply the properties of parallel lines.
Therefore, if we draw a line parallel to DC and passes through B we will find the solution.
And finally we apply the properties of triangles.
∠ A + ∠ B + ∠ D = 180
54 + 110/2 + ∠ D = 180
∠ D = 180 - 54 - 110/2
∠ D = 71
The answer is:
∠ D ≅ 70°