The bookstore has a sales promotion on "October". Each science book is 30 yuan, buy 5 and get 1 free. Uncle Zhang bought 12 books, how much did you spend in total?
书店"十一"搞促销，每本科技书30元，买5本送1本，张叔叔买了12本书，一共用了多少元？
<gadget id="calculator">12 - 2</gadget>
<output>10</output>

<gadget id="calculator">30 * 10</gadget>
<output>300</output>

<result>300</result>