rectangular concrete floor is 18 meters long. If its length is increased by 3 meters, the area will increase by 15 square meters. What is the current area of the concrete floor in square meters?
一块长方形水泥地，长18米，现在把它的长增加3米，面积就会增加15平方米，现在水泥地的面积是多少平方米？
<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<gadget id="calculator">18 * 5</gadget>
<output>90</output>

<gadget id="calculator">90 + 15</gadget>
<output>105</output>

<result>105</result>