Xiaopang borrowed a storybook from the class book corner. He read 15 pages a day for the first 4 days, and 5 more pages a day for the next 6 days. He just finished reading it. How many pages does Xiaopang read on average every day?
小胖从班级图书角借了一本故事书，前4天每天读15页，后6天每天多读5页，正好读完，小胖平均每天读多少页？
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">15 + 5</gadget>
<output>20</output>

<gadget id="calculator">20 * 6</gadget>
<output>120</output>

<gadget id="calculator">60 + 120</gadget>
<output>180</output>

<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">180 / 10</gadget>
<output>18</output>

<result>18</result>