Uncle Liu brought 800 yuan to buy fertilizer, bought 18 bags, and left 80 yuan. How much is the price of each bag of fertilizer?
刘叔叔带800元买化肥，买了18袋，还剩80元．每袋化肥的价钱是多少元？
<gadget id="calculator">800 - 80</gadget>
<output>720</output>

<gadget id="calculator">720 / 18</gadget>
<output>40</output>

<result>40</result>