Now the new regulations: 2.80 yuan per cubic meter for water within 30 cubic meters; 3.80 yuan per cubic meter for more than 30 cubic meters. Last month, the school cafeteria paid 222.70 yuan for water. How much water did the school use last month?
现在新规定：30方以内的水费每方2.80元；超过30方每方3.80元．上个月学校食堂交水费222.70元，学校上月用水多少方？
<gadget id="calculator">2.8 * 30</gadget>
<output>84</output>

<gadget id="calculator">222.7 - 84</gadget>
<output>138.7</output>

<gadget id="calculator">138.7 / 3.8</gadget>
<output>36.5</output>

<gadget id="calculator">36.5 + 30</gadget>
<output>66.5</output>

<result>66.5</result>