There are 20 girls in Class 1, which is equivalent to 80% of boys. How many boys are there?
六一班有女生20人，相当于男生的80%，男生有多少人．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 / (4/5)</gadget>
<output>25</output>

<result>25</result>