spent 26.5 yuan on extracurricular reading materials and 5.6 yuan on stationery. I paid 40 yuan. How much should I get back?
买课外读物用了26.5元，买文具用了5.6元，我付了40元，应找回多少元？
<gadget id="calculator">23.5 - 5.6</gadget>
<output>17.9</output>

<result>17.9</result>