9514 1404 393
Answer:
C. 18 inches
Step-by-step explanation:
The median of a trapezoid is the line segment that joins the midpoints of the sides of the trapezoid. It is halfway between the parallel bases, and is parallel to them. It length is the average of the lengths of the two bases:
(15 +21)/2 = 36/2 = 18 . . . . inches
