Xiaohong spent 16 yuan on books this month, which is 20% less than last month. How much did she spend on books last month?
小红这个月买书花了16元，比上个月节约了20%，上个月买书花了多少钱？
<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">16 / (4/5)</gadget>
<output>20</output>

<result>20</result>