Mom took 100 yuan to the supermarket to shop together. She bought 2 kilograms of meat at 24 yuan per kilogram, and bought 4 bags of biscuits, which cost a total of 48.9 yuan. How much money does mother have left?
妈妈带100元钱到超市共购物，买了2千克肉，每千克24元，又买了4袋饼干共花去48.9元，妈妈还剩下多少钱？
<gadget id="calculator">24 * 2</gadget>
<output>48</output>

<gadget id="calculator">100 - 48 - 48.9</gadget>
<output>3.1</output>

<result>3.1</result>