My brother is learning car driving skills at the Ping An Driving School. The semester lasts for 40 days. My father gives my brother an allowance of 30 yuan per day. If my brother spends 20 yuan a day, how many more days can this pocket money be used than originally planned?
哥哥在平安驾校学习汽车驾驶技术，学期为40天，爸爸每天按30元的标准给哥哥一笔零花钱．如果哥哥每天花20元，这笔零花钱可以比原计划多用多少天？
<gadget id="calculator">40 / 20</gadget>
<output>2</output>

<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<gadget id="calculator">60 - 40</gadget>
<output>20</output>

<result>20</result>