Naughty went to the supermarket to buy stationery and spent a total of 30.8 yuan, of which 9.80 yuan was spent on fountain pens, crayons were 4.5 yuan more expensive than fountain pens, and the remaining money was just enough to buy watercolor pens. How much does it cost to buy watercolor pens?
淘气上超市买文具用共去30.8元，其中买钢笔用去9.80元，蜡笔比钢笔贵4.5元，剩余的钱刚好买水彩笔．买水彩笔用去多少钱？
<gadget id="calculator">9.8 + 4.5</gadget>
<output>14.3</output>

<gadget id="calculator">30.8 - 9.8 - 14.3</gadget>
<output>6.7</output>

<result>6.7</result>