The taxi fare in Shuyang County is 5 yuan for the starting price within 3 kilometers, and 2.5 yuan for every kilometer after 3 kilometers. Aunt Li took a taxi from her home to the Wonderful Supermarket and paid a total of 15 yuan. How many kilometers is the distance from Aunt Li’s home to the Wonderful Supermarket?
沭阳县出租车收费办法是3千米以内收起步价5元，3千米以后每千米另收2.5元．李阿姨乘出租车从家到万得福超市，共付车费15元，李阿姨家到万得福超市有多少千米？
<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<gadget id="calculator">10 / 2.5</gadget>
<output>4</output>

<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<result>7</result>