Explanation:

- We know that x women take 2y days to complete the work, so the total work is 2xy for x women working together.

- Similarly, 1.5x men take y days, meaning the total work here is also 1.5xy.

- For children, 2x children take 3y days, giving us another 6xy for the full work.

- Now, 8 women, 8 men, and 8 children finish the work in 22.5 days.

- The task mentions that 9 men complete it in (y + 20) days, confirming the total work remains consistent under different worker configurations.

- We set equations for each group to find individual rates, realizing that:

- Women, men, and children contribute differently to the total work.

- When combined, 8 women, 8 men, and 8 children complete the work in 22.5 days, with children's rate calculated based on proportional contributions.

- Calculating the portion children accomplish reveals that they complete 12.5% of the work.

- 5. 12.5% is the correct answer.