I just came across this very good source of math drills and wanted to let you know about it.
At https://ca.ixl.com/math/ you can find drills within a number of categories sorted from kindergarden to grade 11.

I liked the system and presentation of the content which looks a lot better then the usual PDF's that come up on a quick google search. So whoever is going for some math basics is welcome to give it a try.

The page demands to become a paying member after a while, but a certain number of drills is free per day.