There are two ropes. The first rope is 13 meters long, which is 2.5 meters longer than the second one. How long is the second rope?
有两根绳子，第一根绳子长13米，比第二根的3倍还要多2.5米．第二根绳子长多少米？
<gadget id="calculator">13 - 2.5</gadget>
<output>10.5</output>

<gadget id="calculator">10.5 / 3</gadget>
<output>3.5</output>

<result>3.5</result>