The school classroom is a rectangle with a known length of 9 meters and a ratio of width to length of 2 meters. How big is the classroom?
学校教室是一个长方形，已知长9米，宽比长短2米，教室的面积有多大？
<gadget id="calculator">9 - 2</gadget>
<output>7</output>

<gadget id="calculator">9 * 7</gadget>
<output>63</output>

<result>63</result>