speedboat and a ship set off from places A and B in the same direction to go to point C respectively. The speedboat is behind and travels 42 kilometers per hour, and the ship travels 34 kilometers per hour. After 2.5 hours, they arrive at point C at the same time. How many kilometers are there between A and B?
一艘快艇和一艘轮船分别从A、B两地同向出发到C地去，快艇在后，每小时行42千米，轮船每小时行34千米，2.5小时后它们同时到达C地，A、B两地相距多少千米？
<gadget id="calculator">42 - 34</gadget>
<output>8</output>

<gadget id="calculator">8 * 2.5</gadget>
<output>20</output>

<result>20</result>