9. (5 points) Li Hua, when buying a certain product, mistakenly read a digit "7" in the unit price as "1", and was preparing to pay 189 yuan, but actually should have paid 147 yuan. It is known that the unit price and the quantity purchased are both integers, then the actual unit price of this product is $\qquad$ yuan, and Li Hua bought $\qquad$ pieces.
【Solution】Solution: $189=3 \times 3 \times 3 \times 7=27 \times 7$
$$
147=3 \times 7 \times 7=21 \times 7
$$

It is exactly $27 \times 7=189$ where 27 is mistaken for $21 \times 7=147$. Therefore, the actual unit price of this product is 21 yuan, and 7 pieces were sold. The answer is: 21,7.