To build a canal with a length of 1,800 meters, team A can build 50 meters per day, and team B can build 40 meters per day. Both teams can build it at the same time. How many days can it be completed?
修一条长1800米得水渠，甲队每天可以修50米，乙队每天可以修40米，两队同时修，多少天可以完成？
<gadget id="calculator">50 + 40</gadget>
<output>90</output>

<gadget id="calculator">1_800 / 90</gadget>
<output>20</output>

<result>20</result>