A total of 90 wheels, after installing 15 bicycles, how many tricycles can be installed on the rest?
一共90个车轮，安装了15辆自行车后，剩下的可以安装多少辆三轮车？
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">90 - 30</gadget>
<output>60</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<result>20</result>