Xiaohua’s water bill this month is 20 yuan, which is 20% less than last month. How much was the water bill last month?
小华家本月的水费是20元，比上月节约了20%，上月的水费是多少元？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 / (4/5)</gadget>
<output>25</output>

<result>25</result>