There are cars, bicycles and motorcycles parked in the parking lot. Among them, the number of cars is equal to the sum of the number of bicycles and 1.5 times the number of motorcycles, and there are 5 fewer motorcycles than bicycles. If there are 15 cars, how many of these three cars are there in the parking lot?
停车场里停有汽车、自行车、摩托车．其中，汽车的辆数等于自行车的辆数与摩托车辆数的1.5倍的和，摩托车比自行车少5辆．若汽车有15辆，则停车场里的这三种车公共有多少辆．
<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<gadget id="calculator">1 + 1.5</gadget>
<output>2.5</output>

<gadget id="calculator">10 / 2.5</gadget>
<output>4</output>

<gadget id="calculator">15 + 4 + 4 + 5</gadget>
<output>28</output>

<result>28</result>