There is a square lawn, and a 1-meter-wide path is built around the lawn. The area of the road is 85 square meters. What is the side length of the lawn?
有一个正方形草坪，给草坪四周向外修1米宽小路，路面面积是85平方米，草坪边长是多少？
<gadget id="calculator">1 * 1 * 4</gadget>
<output>4</output>

<gadget id="calculator">85 - 4</gadget>
<output>81</output>

<gadget id="calculator">81 / 4 / 1</gadget>
<output>81/4 = around 20.25</output>

<result>81/4 = around 20.25</result>