Uncle Liu brought 800 yuan to buy fertilizer, bought 20 bags, and left 20 yuan. How much is each bag of fertilizer?
刘叔叔带了800元钱去买化肥，买了20袋，还剩下20元．每袋化肥多少元？
<gadget id="calculator">800 - 20</gadget>
<output>780</output>

<gadget id="calculator">780 / 20</gadget>
<output>39</output>

<result>39</result>