The distance between two ports, A and B, is 450 kilometers. The fast and slow ships depart from the two ports at the same time. They meet after 9 hours. It is known that the fast ship travels 25 kilometers per hour. How many kilometers per hour does the slow ship travel?
甲乙两港相距450千米，快慢两船同时从两港相对出发，9小时后相遇，已知快船每小时行25千米，慢船每小时行多少千米？
<gadget id="calculator">450 / 9</gadget>
<output>50</output>

<gadget id="calculator">50 - 25</gadget>
<output>25</output>

<result>25</result>