A rectangle has a perimeter of 50 cm and a width of 10 cm. What is the length of this rectangle in centimeters? (solution by equation)
一个长方形的周长是50厘米，宽是10厘米．这个长方形的长是多少厘米？(用方程解)
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">50 - 20</gadget>
<output>30</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<result>15</result>