Xiao Ming buys a pen and 3 pencils, Xiao Gang buys the same 7 pencils, they pay the same amount, how many pencils does the price of a pen equal?
小明买一支钢笔和3支铅笔，小刚买了同样的7支铅笔，他们付出的钱数一样多，一支钢笔价钱等于多少支铅笔？
<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<result>4</result>