Xiao Zhang brought 300 yuan to buy books. She planned to buy 27 books, but there was still a difference of 24 yuan. How much is each book on average?
小张带了300元去买书，她准备买27本，可是还差24元，平均每本书多少钱？
<gadget id="calculator">300 + 24</gadget>
<output>324</output>

<gadget id="calculator">324 / 27</gadget>
<output>12</output>

<result>12</result>