In order to reward the students in the interest group, the teacher spent 92 yuan to buy two books, "Intelligence Challenge" and "Mathematics Fun Questions". It is known that each book of "Intelligence Challenge" is 18 yuan, and each book of "Mathematics Fun Questions" is 8 yuan. Then how many copies of "Mathematics Fun Problems" have you bought?
为了奖励兴趣小组的同学，老师花92元购买了《智力大挑战》和《数学趣题》两种书，已知《智力大挑战》每本18元，《数学趣题》每本8元，则《数学趣题》买了多少本．
<result>7</result>