To determine how much money Dan had in sales last month, we need to know the commission rate. Without that information, we can't calculate the total sales amount accurately.
However, if you are provided with a commission rate (let's say it's "r%", which is a decimal equivalent of the percentage), you can use the formula:
\[ \text{Sales} = \frac{\text{Commission}}{\text{Commission Rate}} = \frac{1900}{r} \]
For example, if Dan's commission rate is 10% (0.10), then his total sales would be:
\[ \text{Sales} = \frac{1900}{0.10} = 19000 \]
If you have the commission rate for this scenario, please provide it, or if you need to assume a standard rate, let me know.