A book, if you read 15 pages a day, you can finish it in 28 days. If you read 20 pages a day, how many days will you finish it?
一本书，如果每天看15页，28天看完．如果每天看20页，几天看完？
<gadget id="calculator">15 / 20</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">28 * (3/4)</gadget>
<output>21</output>

<result>21</result>