Fangfang has been reading a storybook for 6 days, with an average of 15 pages per day. How many pages should she start reading on the 7th day?
芳芳看一本故事书，已经看了6天，平均每天看了15页，第7天应该从多少页看起．
<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">90 + 1</gadget>
<output>91</output>

<result>91</result>