5. In trapezoid $A B C D$ with bases $A D / / B C$, the diagonals intersect at point $E$. It is known that the areas $S(\triangle A D E)=12$ and $S(\triangle B C E)=3$. Find the area of the trapezoid.
Answer: 27

Solution: Triangle ADE and CBE are similar, their areas are in the ratio of the square of the similarity coefficient. Therefore, this coefficient is

![](https://cdn.mathpix.com/cropped/2024_05_06_63faea101299db5464bfg-08.jpg?height=305&width=386&top_left_y=407&top_left_x=1463)