The taxi standard in Wuhan is 8 yuan for the starting price of 3 kilometers (calculated as 3 kilometers if the distance is less than 3 kilometers), and 1.8 yuan per kilometer for the part exceeding 3 kilometers. It took Teacher Zhang a total of 21.5 yuan to take a taxi home from get off work. How many kilometers is it from Teacher Zhang’s home to the school?
武汉市出租汽车标准为起步价3千米收费8元(不足3千米按3千米计算)，超过3千米的部分每千米收费1.8元．一次张老师下班回家坐出租汽车共花了21.5元钱，张老师家到学校有多少千米？
<gadget id="calculator">21.5 - 8</gadget>
<output>13.5</output>

<gadget id="calculator">13.5 / 1.8</gadget>
<output>7.5</output>

<gadget id="calculator">3 + 7.5</gadget>
<output>10.5</output>

<result>10.5</result>