Based on Melody's post in the question you linked, yes, you can find the median by averaging the two parallel sides. It seems like you're having trouble finding the parallel sides.
Call one parallel side x and the other x+7
The area of the trapezoid is the sum of the parallel sides times the height divided by 2 which equals 60 in this case.
\(\frac{h(b_1+b_2)}{2}\)
Since we know the height and the area, we can solve for the sides.
\(\frac{5(x+x+7)}{2}=\frac{10x+35}{2}=60\) From this, we get x=8.5. So we know your work above is correct. Since 1 side is x and the other is x+7, the two parallel sides are 8.5 and 15.5. To find the median, take the average of these two numbers.
