The problem provided involves a geometric figure consisting of a triangle $ABC$ with points $D$ and $E$ marked such that $D$ lies on $AB$ and $E$ lies on $AC$. We have the following given information:

• $|BE| = |EC|$, indicating that $E$ is the midpoint of $AC$.
• $|DB| = 3 \times |AD|$, meaning $D$ divides $AB$ in the ratio 3:1.
• The area of quadrilateral $ADEC$ is 20 square units.

We need to find the area of triangle $DBE$.

Step 1: Calculate |AD| and |DB|: Since $D$ divides $AB$ in the ratio of 3:1, let $|AD| = x$. Therefore, $|DB| = 3x$. Given that $|DB| = 3 \times |AD|$, $|AB| = |AD| + |DB| = x + 3x = 4x$.

Step 2: Ratio of Triangle Areas: Since $E$ is the midpoint of $AC$, $|AE| = |EC|$. This also implies that triangle $AEC$ is twice the area of triangle $AEB$ because they share the same height from $A$ to line $BC$ and $|AE| = |EC|$.

Step 3: Calculate Area of Triangle $AEB$: The area of $ADEC$ is given as 20 units, which is the area of triangle $AEC$ minus triangle $BDE$. Note that quadrilateral $ADEC$ consists of $AEC - BDE$. Triangle $AEC$ is twice the area of $AEB$. So, we need to find the area of triangle $AEB$ from $AEC$ and $BDE$.

Since $AEC$ is twice $AEB$, and $ADEC = AEC - BDE$, and given $ADEC = 20$, we solve as follows:

$AEB = \frac{AEC}{2} = \frac{ADEC + BDE}{2}$

Step 4: Set up the ratio: The area of $AEB$ is a fraction of the area of $ABC$ determined by the ratio $AD:DB$ or $1:3$. If the area of $ABC$ is $S$, then:

$AEB = \frac{1}{4}S$

Step 5: Determine $DBE$ area: Since $DBE$ is part of $AEB$, and $BDE$ is directly subtracted from $AEC$ to get $ADEC$, we consider the ratios and areas involved. Triangle $DBE$ will be smaller compared to $BDE$ due to its relative position and the ratios of division. We look for the area using proportionality:

$\text{If } |AD| = x \text{ and } |DB| = 3x, \text{ then } |AB| = 4x \text{ and }$ $\text{Area of } BDE = \frac{3}{4}S$

$20 = \frac{1}{2}S + \frac{3}{4}S - \text{Area of } BDE$

Given that $E$ splits $AC$ in half, $DBE$ will be smaller compared to $BDE$ by a certain factor due to their shared base $BD$ and similar heights. The area of $DBE$ must be calculated by taking into account its fraction of the larger triangle $AEB$.

Conclusion: With the information given, the best course is to solve the system of equations provided by the area ratios. If you'd like me to provide a specific numerical answer or if there is an error in understanding the setup, please let me know. Further, would you like a more detailed solution to any specific part of this problem?

Here are eight follow-up questions that could help explore this topic further:

1. How does the area of a triangle change when one side is divided into different segments?
2. Can the method used here apply to non-equilateral triangles?
3. What is the significance of a point being the midpoint in triangle area calculations?
4. How does the ratio of line segments within a triangle relate to the areas of the resultant sub-triangles?
5. What other geometric properties could affect the area of triangle $DBE$ if $D$ or $E$ were moved?
6. How can principles of similarity be used to solve other types of geometric problems?
7. What are other examples of problems involving areas of figures composed of triangles and