The density of the residential building equals the amount of workers a similarly density building needs.
Go Karting needs a medium amount of Unskilled workers and a low amount of Skilled workers
An Elementary school needs medium amounts of Skilled and Unskilled.
The amount of housing to support this would be:
2 medium density residential homes for Skilled workers and one each of medium and low density housing for Unskilled
3 low density homes for Skilled workers and 4 low density homes for Unskilled.
I am not clear on how it breaks down and haven't seen anything else posted that shows how it works.