Xiao Zhang’s father took a taxi from home to a certain post office. The starting price of the car was 10 yuan (0-3 kilometers), and every additional 1 kilometer beyond the starting price would be calculated at 1.2 yuan per kilometer. A total of 40 yuan was paid. Please help him calculate, how many kilometers are there from his home to the post office?
小张的爸爸乘坐一辆出租车从家去某邮电局，该车起步价为10元(0--3千米)，超过起步价每增加1千米要按每千米1.2元计算，他爸爸共付了40元．请你帮他算一算，他家到邮电局共有多少千米？
<gadget id="calculator">40 - 10</gadget>
<output>30</output>

<gadget id="calculator">30 / 1.2</gadget>
<output>25</output>

<gadget id="calculator">25 + 3</gadget>
<output>28</output>

<result>28</result>