Also, this is not a standard 5th grade math assignment. To do it purely with logic and no trial and error takes some thought, particularly when getting to the third column with 1, 5, 6, and 7 left over if done as easy as possible.
I solved for the 4, then did 1 instance of trial and error with the top row before I realized there wasn't enough info. I can see how adults that haven't used their minds in decades would have problems with this.
1 7
2 8
9 3
4
5 6? (from top left to bottom right)
Also, this is not a standard 5th grade math assignment. To do it purely with logic and no trial and error takes some thought, particularly when getting to the third column with 1, 5, 6, and 7 left over if done as easy as possible.