Traveling from point A to point B, the express train travels 80 kilometers per hour, and the slow train travels 60 kilometers per hour. The express train leaves 2 hours after the slow train departs. How many hours later will the express train catch up with the slow train?
从A地向B地行驶，快车每小时行80千米，慢车每小时行60千米，慢车出发2小时后，快车才出发，几小时后快车分追上慢车？
<gadget id="calculator">60 * 2</gadget>
<output>120</output>

<gadget id="calculator">80 - 60</gadget>
<output>20</output>

<gadget id="calculator">120 / 20</gadget>
<output>6</output>

<result>6</result>