The price of a "Fairy Tale" book is 1 yuan more than (2/5) of the "Science" book, and the price of a "Fairy Tale" book is 7 yuan. How much is a "Science" book?
一本《童话》书的价钱比《科学》书的(2/5)多1元，一本《童话》书7元，一本《科学》书是多少元．
<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">6 / (2/5)</gadget>
<output>15</output>

<result>15</result>