wire can surround a square with a side length of 10 decimeters. Now use it to surround a rectangle. If the width of this rectangle is 7 decimeters, how many decimeters is the length?
一根铁丝可以围一个边长10分米的正方形，现在用它来围一个长方形，如果这个长方形的宽是7分米，那么长是多少分米？
<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 - 7</gadget>
<output>13</output>

<result>13</result>