Mama Zhang is going to sew lace on a square tablecloth with a side length of 16 decimeters. Now she wants to sew this lace on a rectangular tablecloth with a length of 20 decimeters. It can be used up. The width of this rectangular tablecloth is How many decimeters?
张妈妈准备给一个边长是16分米的正方形桌布缝上花边，现在她要把这条花边改缝在一个长是20分米的长方形桌布上，正好能用完，这个长方形桌布的宽是多少分米？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">16 * 2</gadget>
<output>32</output>

<gadget id="calculator">32 - 20</gadget>
<output>12</output>

<result>12</result>