There are 5 bicycles and tricycles, and a total of 13 wheels. How many tricycles are there?
自行车和三轮车共5辆，总共13个轮子，三轮车有多少辆．
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 - 13</gadget>
<output>2</output>

<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">2 / 1</gadget>
<output>2</output>

<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<result>3</result>