The passenger car and the truck leave from A and B at the same time, go towards each other, and meet after 7 hours. It is known that the speed ratio of the passenger car and the truck is 9:7. When the truck travels 18 kilometers less than the passenger car per hour, then the truck travels from How many hours does it take from place B to place A?
客车和货车同时从甲、乙两地开出，相向而行，7小时后相遇，已知客车和货车的速度比是9：7，当货车每小时比客车少行18千米，那么货车从乙地到甲地需要多少小时？
<gadget id="calculator">9 * 9</gadget>
<output>81</output>

<gadget id="calculator">7 * 9</gadget>
<output>63</output>

<gadget id="calculator">81 + 63</gadget>
<output>144</output>

<gadget id="calculator">144 / 63</gadget>
<output>16/7 = around 2.285714</output>

<gadget id="calculator">7 * (16/7)</gadget>
<output>16</output>

<result>16</result>