Go to a stationery store to buy school supplies. If you buy one pencil and three ballpoint pens, it costs 5 yuan. If you buy three pencils, one ballpoint pen, and four exercise books, it costs 7 yuan. How many yuan can you buy one pencil and one ballpoint pen? and an exercise book.
去文具店买学习用品，如果买一支铅笔三支圆珠笔要5元，如果买三支铅笔一支圆珠笔四本练习本要7元，则用多少元钱就可买到一支铅笔一支圆珠笔和一本练习本．
<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">12 / 4</gadget>
<output>3</output>

<result>3</result>