Fill in all the squares on the board following these rules:
1) The numbers in vertical and horizontal row groups (not entire rows) cannot repeat.
2) The numbers in each horizontal group must add up to the number that appears in the triangle at the far left of the group.
3) The numbers in each vertical group must add up to the number that appears in the triangle at the top of the group.
HINT: Fill in all the single group squares first! See if these lead to any double square groups you can get and so on.
(http://www.coolmath-games.com/0-kakuro/index.html)