The starting price of a taxi in a certain city is 7 yuan (within 3 kilometers), and the average price per kilometer is 2.4 yuan for more than 3 kilometers. Xiao Ming paid a total of 17.8 yuan for the taxi from home to school.
某市出租车起步价为7元(3千米内)，超过3千米，平均每千米为2.4元，小明从家到学校共付车费17.8元，小明家到学校有多少千米？
<gadget id="calculator">17.8 - 7</gadget>
<output>10.8</output>

<gadget id="calculator">10.8 / 2.4</gadget>
<output>4.5</output>

<gadget id="calculator">3 + 4.5</gadget>
<output>7.5</output>

<result>7.5</result>