1. The problem is to fill the numbers 1 to 9 in two 4x4 grids where each row and column forms a valid math equation using addition, subtraction, multiplication, and division. 2. Important rules: - Use each number 1 to 9 exactly once per grid. - Follow order of operations: multiplication and division before addition and subtraction. - Each row and column must satisfy the given equation. 3. For Graph 1 (bottom-left): - The first row equation is $a - b + c = 15$. - The last row equation is $d - e + f = 9$. - Using the numbers 1 to 9, and considering the sums 15 and 9, start by testing combinations. 4. For Graph 2 (bottom-right): - The first row equation is $g - h + i = 10$. - The last row equation is $j + k - l = 11$. - Similarly, test combinations of numbers 1 to 9 to satisfy these equations. 5. After testing and applying the rules, the solutions for the empty spaces in the grids are: Graph 1: - Row 1: 8 - 2 + 9 = 15 - Row 5: 7 - 3 + 5 = 9 Graph 2: - Row 1: 6 - 1 + 5 = 10 - Row 5: 9 + 4 - 2 = 11 These satisfy the equations and use numbers 1 to 9 without repetition. Final answers: - Graph 1 empty spaces: 8, 2, 9, 7, 3, 5 - Graph 2 empty spaces: 6, 1, 5, 9, 4, 2