The taxi charges 8 yuan within 3 kilometers (including 3 kilometers), and 3.5 yuan per kilometer beyond that. How much does Xiaofang need to pay to go from home to a city 15 kilometers away?
出租车3千米之内(含3千米)收费8元，超过的每千米收费3.5元，小芳从家到相距15千米的某城市，需要付车费多少元？
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">3.5 * 12</gadget>
<output>42</output>

<gadget id="calculator">42 + 8</gadget>
<output>50</output>

<result>50</result>