If they get unexpected results they could note what they could've done wrong or what they could change in a next trail of experiments. Or look back and see what different happened to they could've hypothesized. There could be many different courses on what to do next.
The answer is 4.
The easiest way to determine the value of statements like this is to turn the percentage into a decimal and then multiply.
20% * 20
.20 * 20
4
$421,369.20 , I just had this question on Apex.