A section of road has been built, 87 kilometers have been built, which is three times the rest. How many kilometers are left on this road?
修一段路，已经修了87千米，是剩下的3倍．这段路还有多少千米没有修？
<gadget id="calculator">87 / 3</gadget>
<output>29</output>

<result>29</result>