The speed ratio of the two cars is 8:9, the fast car travels 9 km more per hour than the slow car, how many kilometers per hour does the slow car travel?
两辆汽车的速度比是8：9，快车每时比慢车每时多行驶9km，慢车每时行驶多少km．
<gadget id="calculator">9 - 8</gadget>
<output>1</output>

<gadget id="calculator">9 / 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 8</gadget>
<output>72</output>

<result>72</result>