In order to calculate the total sales, knowing that his commission was $450, we can do the following rule of three:
[tex]\begin{gathered} \text{\$450}\to10\text{\%} \\ x\to100\text{\%} \\ \\ \frac{450}{x}=\frac{10}{100} \\ \frac{450}{x}=\frac{1}{10} \\ x=450\cdot10 \\ x=4500 \end{gathered}[/tex]So the total sales was $4500.
