Car A and car B set off from Shanghai to Hangzhou successively. Car A travels an average of 84.5 kilometers per hour, and car B travels an average of 104.5 kilometers per hour. Car A travels 60 kilometers first and then car B sets off. Car B catches up after a few hours A car?
甲、乙两车先后从上海出发去杭州，甲车平均每小时行驶84.5千米，乙车平均每小时行驶104.5千米，甲车先行60千米后乙车出发，几小时后乙车追上甲车？
<gadget id="calculator">104.5 - 84.5</gadget>
<output>20</output>

<gadget id="calculator">60 / 20</gadget>
<output>3</output>

<result>3</result>