Which number replaces the question mark?

Each H-shaped figure has three numbers stacked in a left column and three numbers stacked in a right column, joined by one central number. The rule that governs every complete figure in this set is: Center = |Sum of the left column minus Sum of the right column|.

1. First figure: left column (3, 7, 4) totals 14; right column (9, 2, 1) totals 12; the difference 14 minus 12 = 2 matches the given center value 2.

2. Second figure: left column (1, 5, 4) totals 10; right column (6, 3, 8) totals 17; the difference 17 minus 10 = 7 matches the given center value 7.

3. Third figure: left column (9, 2, 6) totals 17; right column (8, 7, 3) totals 18; the difference 18 minus 17 = 1 matches the given center value 1.

4. The rule reproduces the center value correctly in all three fully known figures without exception, confirming it as the governing pattern.

5. Applying the same rule to the fourth figure: left column (4, 8, 2) totals 14; right column (5, 1, 3) totals 9; the difference 14 minus 9 = 5.

Because the same column-difference rule holds exactly for every one of the three complete figures, it can be trusted for the incomplete one too, confirming that the missing number is 5.