A rectangular flowerbed is 18 meters long and 12 meters wide. If the width is reduced by 3 meters, how many meters should the length be increased to keep the area constant?
一个长方形花圃，长是18米，宽是12米，如果把它宽减少3米，要使面积不变，长应增加多少米？
<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<gadget id="calculator">12 / 9</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">18 * (4/3)</gadget>
<output>24</output>

<gadget id="calculator">24 - 18</gadget>
<output>6</output>

<result>6</result>