Answer: 12 inches
Step-by-step explanation: In this problem, since we're asked to find the length of the median, let's use our formula for the area of a trapezoid that involves the median which is shown below.
Area = median · height
We know that the area is 144 and the height is 9 so we can set up the equation 144 = M · 12. Now to solve for m, we divide both sides of the equation by 12 and we find that 12 = M.
So the length of the median of the trapezoid is 12 inches.