Domogatskikh’s workbooks usually have a solved example at the start of each section.

Solving for the sides of a right-angled triangle (

If you can tell me the or describe the specific task (e.g., "finding the area of a trapezoid with bases 4 and 6"), I can walk you through the step-by-step solution right now.

Using ratios and coefficients of similarity (

Properties of parallelograms, rectangles, rhombuses, and squares.

If you are stuck on a specific page, it likely covers one of these:

Calculating the area of triangles, trapezoids, and polygons.