You can find the step-by-step "GDZ" breakdowns on these reputable educational sites:

Covers advanced stereometry, including volumes and surfaces of revolution. ⚡ Popular Platforms for Solutions

Formal assessments to test unit mastery. Tests: Quick evaluations of theoretical knowledge.

Solutions are available for the entire secondary school cycle:

Focuses on the introduction of stereometry (3D geometry).

Provides digital versions of the manuals alongside the answer keys.