A rope is 42 decimeters long, how many decimeters are left after enclosing it into a square with a side length of 9 decimeters?
一根绳子长42分米，将其围成一个边长9分米的正方形后，还余多少分米．
<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<gadget id="calculator">42 - 36</gadget>
<output>6</output>

<result>6</result>