The distance between the two places is 490 kilometers. Two cars A and B drive towards each other from two places at the same time. Meet in 3.5 hours, car A travels 72 kilometers per hour, how many kilometers per hour does car B travel? (solution by equation)
两地问的路程是490千米．甲、乙两辆汽车同时从两地开出相向而行．3.5小时相遇，甲车每小时行72千米，乙车每小时行多少千米？(用方程解)
<gadget id="calculator">72 * 3.5</gadget>
<output>252</output>

<gadget id="calculator">490 - 252</gadget>
<output>238</output>

<gadget id="calculator">238 / 3.5</gadget>
<output>68</output>

<result>68</result>