There are 39 tricycles and bicycles parked on the playground. The total number of wheels of the two cars is 96. How many tricycles are there?
操场上停放着39辆三轮车和自行车．两种车的轮子总数是96个．三轮车有多少辆．
<gadget id="calculator">39 * 3</gadget>
<output>117</output>

<gadget id="calculator">117 - 96</gadget>
<output>21</output>

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

<gadget id="calculator">21 / 1</gadget>
<output>21</output>

<gadget id="calculator">39 - 21</gadget>
<output>18</output>

<result>18</result>