There are a total of 30 cars with 4 wheels and three-wheeled motorcycles with three wheels parked in the parking lot. These cars have a total of 100 wheels, so how many three-wheeled motorcycles are there?
停车场里停放着4个轮子的汽车和3个轮子的三轮摩托车共30辆，这些车共有100个轮子，那么三轮摩托车有多少辆．
<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">100 - 90</gadget>
<output>10</output>

<gadget id="calculator">4 - 3</gadget>
<output>1</output>

<gadget id="calculator">10 / 1</gadget>
<output>10</output>

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

<result>20</result>