The optional equipment for assembling 30 cars in a certain factory is: radio, air conditioner and intercom. It is known that 15 of them have radios, 8 have air conditioners, and 6 have intercoms, and 3 of them have all three types of equipment. ． May I ask at least how many cars do not offer any equipment?
在某工厂装配30辆汽车可供选择的设备是：收音机、空调和对讲机，已知其中15辆汽车有收音机，8辆有空调，6辆有对讲机，而且其中3辆汽车这三样设备都有．请问至少有多少辆汽车没有提供任何设备？
<gadget id="calculator">8 - 3</gadget>
<output>5</output>

<gadget id="calculator">15 + 5</gadget>
<output>20</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<result>10</result>