Mom goes to the store to buy things. She spends half of the money she brings on clothes, 5.1 yuan on stationery, and half of the remaining money on pens. At this time, there is 2.1 yuan left. How much did mother bring to the store? money?
妈妈去商店买东西，她买衣服用去所带钱的一半，买文具用去5.1元，买钢笔又用去余下钱的一半，这时还剩2.1元，妈妈去商店时一共带了多少元钱？
<gadget id="calculator">2.1 * 2</gadget>
<output>4.2</output>

<gadget id="calculator">4.2 + 5.1</gadget>
<output>9.3</output>

<gadget id="calculator">9.3 * 2</gadget>
<output>18.6</output>

<result>18.6</result>