Originally Posted by

**ssuag** We'll solve it a piece at a time. I'd suggest filling it in as we go along.

Row Y must be all zeros to get that total.

The remaining three cells in the first column must all be 5; this is the only way to get a total of 15 at the bottom of the column (given that one cell must be zero). So the first cell in column X must be 5.

Since the first cell in row W is now 5, the remaining cells have to be zero in order for the final row total to be 5.

Now rows W and Y both have zeros in the fourth column. Since the column total is 10, the only possibility is that the fourth cells in both X and Z must be the maximum allowed value of 5.

The only blanks left are the second boxes in rows X and Z. The second Z box must be 5 (but this is unimportant to us). The second X box has to be three in order to get a total of 13, since the other boxes are 5, 0, and 5.

This gives us a final order for row X as 5, 3, 0, 5, which is the answer for A.