10. (6 points) In stores A and B, the marked price of a certain commodity is the same. Store A sells this commodity at the marked price, with sales amounting to 7200 yuan; Store B sells it at an 80% discount of the marked price, selling 15 more items than Store A, with the same sales amount as Store A. Then, Store A sold $\qquad$ items of this commodity.
【Solution】Solution: The money earned by Store B from selling 15 items:
$$
\begin{array}{l}
7200-7200 \times 80\%, \\
=7200-5760, \\
=1440 \text { (yuan), }
\end{array}
$$

The price of one item:
$$
\begin{array}{l}
1440 \div 15 \div 80\%, \\
=96 \div 0.8, \\
=120 \text { (yuan), }
\end{array}
$$

The number of items sold by Store A: $7200 \div 120=60$ (items), Answer: Store A sold 60 items of this product. Therefore, the answer is: 60.