A rectangular lawn with a length of 54 meters and a width of 30 meters, if the length of the lawn is reduced by 18 meters, how many meters should the width be increased to keep the area of the lawn unchanged?
一块长54米，宽30米的长方形草坪，把草坪的长减少18米，宽应该增加多少米草坪的面积不变？
<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">90 - 30</gadget>
<output>60</output>

<result>60</result>