rectangle is 15 cm long. If the length is reduced by 5 cm, it becomes a square. What is the perimeter of this rectangle in centimeters?
一个长方形，长15厘米．如果长减少5厘米，就变成一个正方形．这个长方形的周长是多少厘米？
<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<gadget id="calculator">15 + 10</gadget>
<output>25</output>

<gadget id="calculator">25 * 2</gadget>
<output>50</output>

<result>50</result>