John arm wrestles 20 people.  He beats 80%.  How many people did he lose to?
He beats 20*.8=
<gadget id="calculator">20*.8</gadget>
<output>16</output>
16 people.
So he loses to 20-16=
<gadget id="calculator">20-16</gadget>
<output>4</output>
4 people.

<result>4</result>