In order to encourage residents to save water, this year Beijing began to implement tiered fees, the first level being that the annual water consumption does not exceed 180 tons. The charge is 5 yuan per ton, and the second grade with an annual water consumption of more than 181 tons is charged at 7 yuan per ton. The water fee for Liangliang’s family last year was 1404 yuan. How many tons did Liangliang’s family use last year?
为了鼓励居民节约用水，今年北京开始实施阶梯收费，第一档为年用水量不超过180吨．按5元/吨来收，第二档年用水量181吨以上的，按7元/吨来收，亮亮家去年的水费是1404元，亮亮家去年用水多少吨？
<gadget id="calculator">180 * 5</gadget>
<output>900</output>

<gadget id="calculator">1_404 - 900</gadget>
<output>504</output>

<gadget id="calculator">504 / 7</gadget>
<output>72</output>

<gadget id="calculator">180 + 72</gadget>
<output>252</output>

<result>252</result>