Mr. Lin took 90 yuan to buy the newly published Haha Pictorial, but found that if he bought 9 copies, there was still 9 yuan short. How much is each book of this kind?
林老师带90元去买新出版的哈哈画报，结果发现买9本的话还缺9元，这种书每本多少元？
<gadget id="calculator">90 + 9</gadget>
<output>99</output>

<gadget id="calculator">99 / 9</gadget>
<output>11</output>

<result>11</result>