First, I'll examine the first row. I notice that the corners already contain 2 and 3. Since each row must include the numbers 1, 2, 3, and 4 without repetition, the missing numbers in the first row must be 1 and 4.
Next, I'll look at the first column. The top-left cell is 2, and the bottom-left cell is 1. This means the remaining cells in the first column must be 3 and 4.
Moving on to the second row, the leftmost cell is 1, and there's already a 2 in the third column. To avoid repetition, the missing numbers in this row should be 3 and 4.
In the third row, the leftmost cell is empty, and there's a 1 in the second column and a 3 in the third column. This suggests that the missing numbers here are 2 and 4.