Dongsheng Primary School used 285 tons of water in October, 30 tons more than in September. How many tons of water does this primary school use in two months?
东升小学十月份用水285吨，比九月份多用30吨，这所小学两个月共用水多少吨？
<gadget id="calculator">285 - 30</gadget>
<output>255</output>

<gadget id="calculator">255 + 285</gadget>
<output>540</output>

<result>540</result>