Xiaohong took 20 yuan to buy books. The unit price of "Story King" was 5.50 yuan, and the unit price of "Mysterious Detective" was 12.45 yuan. Xiaohong buys one copy each, how much money is left?
小红拿着20元去买书，《故事大王》单价5.50元，《神秘侦探》单价12.45元．小红各买一本，还剩多少钱？
<gadget id="calculator">20 - 5.5 - 12.45</gadget>
<output>2.05</output>

<result>2.05</result>