Xiaohong bought a set of four famous books at a discounted price of 15%, which is 18 yuan cheaper than the original price. What is the original price of this set of four famous books?
小红按八五折的优惠价买了一套四大名著，比原价便宜了18元，这套四大名著原价是多少元．
<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">1 - (17/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">18 / (3/20)</gadget>
<output>120</output>

<result>120</result>