Teacher Wang bought 4 fountain pens and 6 ballpoint pens, and spent a total of 52 yuan. It is known that a fountain pen costs 3 yuan more than a ballpoint pen. How much is the unit price of the pen?
王老师买了4支钢笔和6支圆珠笔，共花去52元．已知1支钢笔比1支圆珠笔贵3元．钢笔的单价是多少元？
<gadget id="calculator">3 * 6</gadget>
<output>18</output>

<gadget id="calculator">18 + 52</gadget>
<output>70</output>

<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">70 / 10</gadget>
<output>7</output>

<result>7</result>