Each pen is 12 yuan, and each ballpoint pen is 7 yuan. A total of 6 pens were bought, and 52 yuan was used. How many pens did you buy?
钢笔每枝12元，圆珠笔每枝7元，共买了6枝笔，用了52元，买了多少枝钢笔．
<gadget id="calculator">6 * 7</gadget>
<output>42</output>

<gadget id="calculator">52 - 42</gadget>
<output>10</output>

<gadget id="calculator">12 - 7</gadget>
<output>5</output>

<gadget id="calculator">10 / 5</gadget>
<output>2</output>

<result>2</result>