The school shipped 3 trucks of cement, each with 180 bags. 320 bags have been used, how many bags are left?
学校运来3车水泥，每车180袋．用去320袋，还剩多少袋？
<gadget id="calculator">180 * 3</gadget>
<output>540</output>

<gadget id="calculator">540 - 320</gadget>
<output>220</output>

<result>220</result>