Li Jia saved 19.4 yuan of pocket money in April. He wanted to buy 4 books for the children in the disaster area, each of which was 7.5 yuan. How much money is left?
李佳4月份节省零用钱19.4元，他想为灾区小朋友购买4本图书，每本7.5元，还差多少钱？
<gadget id="calculator">7.5 * 4</gadget>
<output>30</output>

<gadget id="calculator">30 - 19.4</gadget>
<output>10.6</output>

<result>10.6</result>