The blank space to form a linear pair with m∠BPD is m∠APD.
What are linear pair angles?
Linear pair of angles are formed when two lines intersect each other at a single point.
Linear pair angles are adjacent to each other.
Therefore, the sum of a linear pair angles is equals to 180 degrees.
This means linear pair angles are supplementary.
Hence,
m∠APD + m∠BPD = 180°
learn more on linear pair angles here: https://brainly.com/question/26555759
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