Xiaohong wants to use her pocket money to buy a 20-yuan racket. She has already saved 15.3 yuan. How much pocket money does she need to save to buy it?
小红想用零花钱买一付20元的球拍，她已经攒了15.3元，她还需要攒多少元零花钱才能购买．
<gadget id="calculator">20 - 15.3</gadget>
<output>4.7</output>

<result>4.7</result>