One rope is 1.8 meters long and the other rope is 1.5 meters long. When the two ropes are joined together, the length is 3 meters. What is the length of the joint?
一根绳子长1.8米，另一根绳子长1.5米，把两根绳子接在一起后的长度是3米，接头处是多少米．
<gadget id="calculator">1.8 + 1.5</gadget>
<output>3.3</output>

<gadget id="calculator">3.3 - 3</gadget>
<output>0.3</output>

<result>0.3</result>