Teacher Liu brought 500 yuan to buy the same thing, bought 20 bags, and left 50 yuan. How much is each bag?
刘老师带500元钱买同一种东西，买了20袋，剩下50元．每袋东西是多少？
<gadget id="calculator">500 - 50</gadget>
<output>450</output>

<gadget id="calculator">450 / 20</gadget>
<output>45/2 = around 22.5</output>

<result>45/2 = around 22.5</result>