A bouquet of flowers is 20 yuan, buy 4 bouquets and get 1 free. Aunt Li buys 4 bouquets at a time, how much is each bouquet cheaper?
一束鲜花20元，买4束送一束，李阿姨一次买4束，每束便宜多少钱？
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">80 / 5</gadget>
<output>16</output>

<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<result>4</result>