pen is 5.60 yuan, and a pencil case is 7.80 yuan. Xiaoli bought a pen and a pencil case and paid 15 yuan. How much should she get back?
一枝钢笔5.60元，一个文具盒7.80元，小丽买了一枝钢笔和一个文具盒，付出15元，应找回多少元？
<gadget id="calculator">5.6 + 7.8</gadget>
<output>13.4</output>

<gadget id="calculator">15 - 13.4</gadget>
<output>1.6</output>

<result>1.6</result>