I find this boring.... But opinions may differ. You can't do a sum more than _+_=_. For example you can't do __+__=__ because not enough squares horizontally, I may be wrong in this. Also doesn't really test your math skills, I think.
Digitron ? Veoma cudna rec zas kalkulator :)
Great Awesome game
Modern Car Drive Parking! Car Block Sliding Puzzler- Slide and solve the puzzles