Mom goes to the supermarket and buys a toothbrush for 4.6 yuan and a towel for 8.7 yuan. She pays 15 yuan. How much should she get back?
妈妈到超市，买一支牙刷用去4.6元，买一条毛巾用去8.7元，她付出15元，应找回多少元？
<gadget id="calculator">4.6 + 8.7</gadget>
<output>13.3</output>

<gadget id="calculator">15 - 13.3</gadget>
<output>1.7</output>

<result>1.7</result>