Xiaoliang and his father went to Houyi Park to play, and the price was 4 yuan within 3 kilometers, and the price was increased by 1 yuan for every kilometer beyond 3 kilometers. When they got off the bus, their father paid 12 yuan. How many kilometers did they travel by taxi?
小亮和爸爸去后羿公园玩，3千米以内计价4元，超过3千米，每千米加价一元，下车时，爸爸付了12元，他们坐出租车行了多少千米？
<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<gadget id="calculator">8 / 1</gadget>
<output>8</output>

<gadget id="calculator">3 + 8</gadget>
<output>11</output>

<result>11</result>