To calculate the commission Sadie earned, you can use the following formula:
\[ \text{Commission} = \text{Sale price} \times \text{Commission rate} \]
In this case, the sale price is $730.75 and the commission rate is 4% (or 0.04 in decimal form).
Now, calculate the commission:
\[ \text{Commission} = 730.75 \times 0.04 = 29.23 \]
So, Sadie earned $29.23 in commission.