18 meters of a rope have been used up, and the rest is 21 meters more than what was used. How many meters was the rope originally?
一根绳子用去了18米，剩下的比用去的多21米，这根绳子原来有多少米？
<gadget id="calculator">18 + 21 + 18</gadget>
<output>57</output>

<result>57</result>