Little Buddy can get 3 dollars a day for doing housework, and 5 dollars a day if he does a particularly good job. In one month (30 days), he earned a total of $100. How many days did he do particularly well this month?
小布迪做家务，每天可得3美元，做得特别好时每天可得5美元．有一个月(30天)他一共得了100美元，这个月他有多少天做得特别好？
<gadget id="calculator">3 * 30</gadget>
<output>90</output>

<gadget id="calculator">100 - 90</gadget>
<output>10</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<result>5</result>