Geometry

Question Analysis:
This tests application of the midsegment length formula.

Key Concept Explanation:
The midsegment (median) of a trapezoid is parallel to the bases and equals their average length: M = (b₁ + b₂)/2

Step-by-Step Solution:
Plug known values into formula:
15 = (20 + AB)/2
Solve algebraically:
30 = 20 + AB
AB = 10

Common Mistakes:
F...