Xiao Ming bought two books, "Grimm's Fairy Tales" for 18.5 yuan, 7.5 yuan more than "Xinhua Dictionary". Xiao Ming gave the salesperson 30 yuan, how much should he get back?
小明买了两本书，《格林童话》18.5元，比《新华字典》多7.5元．小明给了售货员30元，应找回多少元？
<gadget id="calculator">18.5 - 7.5</gadget>
<output>11</output>

<gadget id="calculator">30 - 18.5 - 11</gadget>
<output>0.5</output>

<result>0.5</result>