To solve this, let's assume the following variables for the figure based on the problem statement:

1. CD || AB: This tells us that CD is parallel to AB.
2. AD = BD: This means the segment AD is equal in length to the segment BD.
3. b = $\frac{2}{5}$a: The value of $b$ is two-fifths of $a$.

Step-by-step approach:

1. AD = BD suggests that triangle ABD is isosceles.
2. Since $b = \frac{2}{5}a$, the value of $b$ depends directly on $a$.
3. The relationships between the angles in the isosceles triangle will help solve for $a$, $b$, and $c$, but without the exact figure and additional angle values, it's difficult to proceed.

Could you upload the figure or describe it in more detail, especially if there are angle measurements or more information related to triangle properties?

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Meanwhile, here are 5 related questions that could help deepen your understanding:

1. What are the properties of an isosceles triangle?
2. How do you find angles in a triangle when given a proportional relationship between sides?
3. What is the sum of the interior angles in any triangle?
4. How does parallelism affect the angles and side lengths in geometric figures?
5. How do you solve for one variable in terms of another using ratios?

Tip: In geometry, always look for symmetries and parallelism to simplify angle and side length relationships.