Xiaohong spent 30 yuan on books last month, accounting for 20% of the total expenditure. How much did Xiaohong spend last month?
小红上月买书花了30元，占总支出的20%，小红上个月一共用了多少元？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">30 / (1/5)</gadget>
<output>150</output>

<result>150</result>