On Children's Day, Zhang Hua spent 0.6 yuan less to buy 4 pens than to buy 1 extra-curricular book. The price of each pen is 2.5 yuan. How much is the price of each extra-curricular book? (column equation solution)
"六一"儿童节，张华买4枝笔比买1本课外书少花钱0.6元，每枝笔价格2.5元，每本课外书价格多少元？(列方程解答)
<gadget id="calculator">4 * 2.5</gadget>
<output>10</output>

<gadget id="calculator">10 + 0.6</gadget>
<output>10.6</output>

<result>10.6</result>