The teacher brought money to buy 14 pencils and 12 exercise books, which were just used up. If you buy 20 pencils and 10 exercise books, they will be used up. If the teacher buys pencils with all the money he brings, how many pencils can he buy?
老师带的钱买14支铅笔和12本练习本，正好用完．如果买20支铅笔和10本练习本，也正好用完．如果老师把带的钱全部买铅笔，可以买多少支．
<gadget id="calculator">12 * 3</gadget>
<output>36</output>

<gadget id="calculator">14 + 36</gadget>
<output>50</output>

<result>50</result>