I'm trying to solve the following quiz from my daily quiz calendar (I have it in paper so I cannot give a link). It's like a crossword puzzle but with numbers.
The empty cells should be filled with numbers from 1-9 and should be the green cells in sum.
19 = 7+7+5 is prefilled. And the 4 in 11=7+4 is filled from me.
I tried to solve it with a linear equation system but I failed.
Does anybody have tips on how to solve this?