The football field in the school is a rectangle with a width of 21.5 meters, and its perimeter is 223 meters. Find the length of the football field (use the equation to solve it).
学校的足球场是宽21.5米的长方形，它的周长是223米，求出足球场的长是多少(用方程解)．
<gadget id="calculator">21.5 * 2</gadget>
<output>43</output>

<gadget id="calculator">223 - 43</gadget>
<output>180</output>

<gadget id="calculator">180 / 2</gadget>
<output>90</output>

<result>90</result>