A box of chocolates is 25.50 yuan, a box of biscuits is 15.5 yuan, mother buys two boxes of chocolates and two boxes of biscuits with 100 yuan, how much should I get back?
一盒巧克力25.50元，一盒饼干15.5元，妈妈用100元买两盒巧克力和两盒饼干，应找回多少元？
<gadget id="calculator">25.5 * 2</gadget>
<output>51</output>

<gadget id="calculator">15.5 * 2</gadget>
<output>31</output>

<gadget id="calculator">51 + 31</gadget>
<output>82</output>

<gadget id="calculator">100 - 82</gadget>
<output>18</output>

<result>18</result>