A frog eats 80 pests every day, and a swallow eats 20 fewer pests than the frog (3/4). How many pests does a swallow eat every day?
一只青蛙每天吃害虫80只，一只燕子比青蛙的(3/4)少20只，一只燕子每天吃害虫多少只？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">80 * (3/4)</gadget>
<output>60</output>

<gadget id="calculator">60 - 20</gadget>
<output>40</output>

<result>40</result>