Xiaoya used 30 yuan to buy 3 fountain pens, and the money she got back could just buy 5 notebooks with a unit price of 3 yuan. How much is the unit price of the fountain pen Xiaoya bought?
小亚用30元买了3支水笔，找回的钱正好可以买5本单价为3元的笔记本．小亚买的水笔的单价是多少元？
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">30 - 15</gadget>
<output>15</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<result>5</result>