Xiao Dingding bought 15 exercise books, Xiaopang bought 18 exercise books, Xiao Dingding paid 36 yuan less than Xiaopang, how much is each exercise book?
小丁丁买了15本练习本，小胖买了18本练习本，小丁丁比小胖少付36元，每本练习本多少元？
<gadget id="calculator">18 - 15</gadget>
<output>3</output>

<gadget id="calculator">36 / 3</gadget>
<output>12</output>

<result>12</result>