A, B, and C each get 9 yuan to buy exercise books, because A gets 15 less books than C, and B gets as much as C, so both B and C have to give A 1.5 yuan, how much is an exercise book.
甲乙丙各拿9元钱买练习本，由于甲比丙少拿15本，乙拿的与丙同样多，这样乙和丙两个人都要给甲1.5元，一本练习本多少元．
<gadget id="calculator">9 + 1.5</gadget>
<output>10.5</output>

<gadget id="calculator">1.5 * 2</gadget>
<output>3</output>

<gadget id="calculator">9 - 3</gadget>
<output>6</output>

<gadget id="calculator">10.5 - 6</gadget>
<output>4.5</output>

<gadget id="calculator">4.5 / 15</gadget>
<output>0.3</output>

<result>0.3</result>