1. The problem is to find the value of the missing number $?$ in the equation $1 + ? - ... = -1$ given the other rows and columns. 2. From the first row: $2 - 3 + 5 = 4$. 3. From the third row: $8 + 4 + 6 = 18$. 4. From the last row, the numbers are $-5$, $14$, and $20$ in columns 1, 3, and 5 respectively. 5. The second and fourth rows contain plus signs and empty cells, indicating sums of columns. 6. Let's analyze the columns using the last row as sums: - Column 1: $2 + 8 + 1 = ?$ should equal $-5$. Calculate: $2 + 8 + 1 = 11$, but sum is $-5$, so the missing value in the second row, first column must be $-16$ to make $2 + (-16) + 8 + 1 = -5$. - Column 3: $3 + 4 + ? = 14$. Calculate $3 + 4 = 7$, so $7 + ? = 14$ implies $? = 7$. - Column 5: $5 + 6 + ... = 20$. Calculate $5 + 6 = 11$, so $11 + ... = 20$ implies $... = 9$. 7. Now, check the third row equation: $1 + ? - ... = -1$. Substitute $?$ and $...$: $$1 + 7 - 9 = 1 + 7 - 9 = -1$$ This satisfies the equation. 8. Therefore, the missing number $?$ is $7$. Final answer: $7$