The bookstore has a sales promotion on "October". Each science book is 42 yuan, buy 6 and get 1 free. Aunt Zhang bought 14 books, how much did she spend in total?
书店"十一"搞促销，每本科技书42元，买6本送1本，张阿姨买了14本书，一共用了多少元？
<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">42 * (6/7) * 14</gadget>
<output>504</output>

<result>504</result>