Final answer:
The segment addition postulate states that the distance between two points is equal to the sum of the distances between those points and a third point. Using this postulate, we can solve for 2pq by substituting pq + qr for pr in the given equation. The correct answer is D) 2pr - qr.
Step-by-step explanation:
The segment addition postulate states that if three points A, B, and C are collinear, then the distance between A and C is equal to the sum of the distances between A and B, and B and C. In equation form, it is expressed as AC = AB + BC.
In this question, we are given that pq + qr = pr. If we want to find 2pq, we can use the segment addition postulate and substitute pq + qr for pr, giving us 2pq = pr - qr. Therefore, the correct answer is D) 2pr - qr.