A technical book, read 15 pages per hour, and finish it in 6 hours; if you read 3 more pages per hour, how many hours can you finish it?
一本科技书，每小时看15页，6小时看完；如果每小时多看3页，几小时可以看完？
<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">15 + 3</gadget>
<output>18</output>

<gadget id="calculator">90 / 18</gadget>
<output>5</output>

<result>5</result>