A rectangle whose perimeter is 50 decimeters has a length of 19 decimeters, what is its width in decimeters?
周长是50分米的长方形，长是19分米，它的宽是多少分米．
<gadget id="calculator">50 / 2</gadget>
<output>25</output>

<gadget id="calculator">25 - 19</gadget>
<output>6</output>

<result>6</result>