Xiaoqiang reads a literary classic. If he reads 20 pages a day, he can finish it in 18 days. If he reads 5 pages less a day, how many days can he finish it?
小强读一本文学名著，如果每天读20页，18天可以读完，如果每天少读5页，几天可以读完？
<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<gadget id="calculator">18 / 15</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">20 * (6/5)</gadget>
<output>24</output>

<result>24</result>