The bookstore launched a discount card in the promotional activities, each card is priced at 20 yuan, and you can enjoy a 20% discount with the card. Once, Li Ming went to the bookstore to buy books. When checking out, he bought the discount card first. If you saved 12 yuan, how much cash did Li Ming pay for the book purchase?
书店在促销活动中，推出一种优惠卡，每张卡售价20元，凭卡可享受八折优惠，有一次，李明同学到该书店购书，结账时，他先买了优惠卡，结果节省了12元，那么李明同学此次购书时所付的现金是多少元．
<gadget id="calculator">20 + 12</gadget>
<output>32</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">32 / (1/5)</gadget>
<output>160</output>

<gadget id="calculator">160 - 32</gadget>
<output>128</output>

<result>128</result>