The school pays 255 yuan for water in May, saving 15% compared with April. How much is the water fee for April?
学校五月份付水费255元，比四月份节约15%，四月份付水费多少元．
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 - (3/20)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">255 / (17/20)</gadget>
<output>300</output>

<result>300</result>