In order to encourage residents to save water, the water company stipulates that each household will be charged 2.2 yuan per ton for water up to 5 tons (including 5 tons) per month, and 3 yuan per ton for more than 5 tons. A total of 20 yuan was paid for the water. Do you know how many tons Wen Wenjia used last month? The equation can be solved.
为鼓励居民节约用水，自来水公司规定，每户每月用水5吨以内(含5吨)，按每吨2.2元收费，超过5吨的吨数按每吨3元收费，文文家上个月共交水费20元，你知道文文家上个月用水多少吨吗？可列方程解答．
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">2.2 * 5</gadget>
<output>11</output>

<gadget id="calculator">20 - 11</gadget>
<output>9</output>

<gadget id="calculator">15 + 9</gadget>
<output>24</output>

<gadget id="calculator">24 / 3</gadget>
<output>8</output>

<result>8</result>