Xiaobing's mother went to the supermarket to buy 3 bags of snow cakes, each bag was priced at 15.8 yuan, and a toy car was 81.8 yuan. If he only had 100 yuan, how much money would he need to buy back these things?
小兵的妈妈到超市买3袋雪饼，每袋售价为15.8元，一辆玩具小车81.8元，如果他只有100元，还差多少元才能买回这些东西？
<gadget id="calculator">15.8 * 3</gadget>
<output>47.4</output>

<gadget id="calculator">100 - 47.4</gadget>
<output>52.6</output>

<gadget id="calculator">81.8 - 52.6</gadget>
<output>29.2</output>

<result>29.2</result>