A, B, and C each took out 9 yuan to buy a batch of exercise books together. Since B took 15 more books than A, and C took the same amount more than B, both B and C should give A 1.5 yuan, how many exercise books did the three people buy together?
甲、乙、丙三人各拿出9元钱合买了一批练习本，由于分配时乙比甲多拿了15本，丙比乙多拿得同样多，因此乙和丙都要给甲1.5元，那么三人合买了多少本练习本．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">15 * (2/3)</gadget>
<output>10</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<gadget id="calculator">1.5 / 5</gadget>
<output>0.3</output>

<gadget id="calculator">3 / 0.3</gadget>
<output>10</output>

<gadget id="calculator">9 * 10</gadget>
<output>90</output>

<result>90</result>