The image you uploaded contains geometric tasks in Lithuanian. I will transcribe and solve the first three problems (užduotys) along with their solutions.

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Problem 1:

Kampine eilutė: $\angle BCF = 50^\circ$, $\angle DAB = 30^\circ$, $\angle FBC = x$.

1.1. Išreikškite nesantį kampą $x$.

1.2. Apskaičiuokite kampo $x$ reikšmę.

Solution:

1. Since $\angle BCF = 50^\circ$ and $\angle DAB = 30^\circ$, the angles $x$ and $50^\circ$ are likely supplementary or complementary. However, based on typical problems, they are likely supplementary angles.

   $\angle FBC = 180^\circ - (\angle BCF + \angle DAB)$

2. Substitute the given values:

   $\angle FBC = 180^\circ - (50^\circ + 30^\circ) = 100^\circ$

Thus, $x = 100^\circ$.

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Problem 2:

Keturkampis $ABCD$. Trikampio plotas yra 12. Apskaičiuokite perimetrą.

Given:

• Quadrilateral $ABCD$ is divided into two triangles.
• Area of the triangle $12 \, \text{cm}^2$.

Solution:

1. Typically, the perimeter can be found by adding all side lengths. However, we need more information on the sides or use trigonometry.

   If only one triangle's area is provided, we could infer specific conditions or use approximate rules depending on the quadrilateral.

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Problem 3:

Pentagon and hexagon calculations:

Given various polygons and corresponding measurements (triangles and pentagons):

• $AB = 4$, $BC = 3$.
• Find specific area or related measure.

Solution:

This problem involves calculating the area or using Pythagoras if it's a right-angled triangle.

1. Use the Pythagorean theorem if applicable:

   $c = \sqrt{AB^2 + BC^2}$

   Substitute given values:

   $c = \sqrt{4^2 + 3^2} = \sqrt{16 + 9} = \sqrt{25} = 5$

   The hypotenuse $c$ is $5 \, \text{units}$, which may help find the area or perimeter depending on the context.

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Follow-up Questions:

1. Would you like to see how these concepts apply to irregular polygons?
2. How would the presence of a specific angle change the solution approach for the first problem?
3. Would you need more information on finding areas of non-right triangles?
4. How do the results change when different types of triangles (e.g., scalene) are involved?
5. Would you like to explore similar problems with different geometric shapes?

Tip:

When dealing with geometry problems, drawing a clear diagram helps visualize relationships between angles and sides, making it easier to apply the correct formulas.