An agent sold a piece of land for Kshs 2,500,000. The seller received Kshs 2,000,000 after the agent's commission. Calculate the agent's commission as a percentage of the selling price.

The agent's commission is the difference between the selling price of the land and the amount the seller received.

$$\text{Agent's Commission} = \text{Selling Price} - \text{Amount Received by Seller}$$ $$\text{Agent's Commission} = \text{Kshs } 2,500,000 - \text{Kshs } 2,000,000$$ $$\text{Agent's Commission} = \text{Kshs } 500,000$$

The percentage commission is calculated by dividing the agent's commission by the total selling price and multiplying by 100%.

$$\text{Percentage Commission} = \frac{\text{Agent's Commission}}{\text{Selling Price}} \times 100\%$$ $$\text{Percentage Commission} = \frac{\text{Kshs } 500,000}{\text{Kshs } 2,500,000} \times 100\%$$ $$\text{Percentage Commission} = \frac{5}{25} \times 100\%$$ $$\text{Percentage Commission} = \frac{1}{5} \times 100\%$$ $$\text{Percentage Commission} = 0.2 \times 100\%$$ $$\text{Percentage Commission} = \boxed{20\%}$$