In order to protect water resources, a certain city stipulates that the water consumption per person per month should not exceed 2 tons, 1.2 yuan per ton, and more than 2 tons, 3 yuan per ton. There are three people in the Huanhuan family. How many tons of water did Huanhuan use last month?
为了保护水资源，某市规定：每人每月用水量不超过2吨，每吨1.2元，超过2吨，每吨3元，欢欢家有三口人，上月共缴水费18元，上月欢欢家用水多少吨．
<gadget id="calculator">1.2 * 2</gadget>
<output>2.4</output>

<gadget id="calculator">18 - 2.4</gadget>
<output>15.6</output>

<gadget id="calculator">15.6 / 3</gadget>
<output>5.2</output>

<gadget id="calculator">5.2 + 2</gadget>
<output>7.2</output>

<result>7.2</result>