To assemble 210 computers, it has been installed for 6 days, 15 computers are assembled every day, and the remaining 20 computers are assembled every day. How many days will it take to finish the installation?
要装配210台电脑，已经装了6天，每天装配15台，剩下的每天装配20台，还要几天才能装完？
<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">210 - 90</gadget>
<output>120</output>

<gadget id="calculator">120 / 20</gadget>
<output>6</output>

<result>6</result>