To find the dollar amount of David's sales based on his commission, you can use the following formula:
\[ \text{Commission} = \text{Sales} \times \text{Commission Rate} \]
In this case, the commission is $7500 and the commission rate is 4% (or 0.04 in decimal form). We can rearrange the formula to solve for sales:
\[ \text{Sales} = \frac{\text{Commission}}{\text{Commission Rate}} \]
Now, plug in the values:
\[ \text{Sales} = \frac{7500}{0.04} = 187,500 \]
Thus, the dollar amount of David's sales is $187,500.