What will come in place of the question mark (?) in the following question?…

Laws of surds and indices: for a perfect square a, √a is the positive integer whose square equals a. To solve for an unknown under a root, first evaluate every surd and power (like 9², 13²) on both sides, then move all known terms to one side to isolate the root, and finally square both sides to remove it.

1. Evaluate the surds: √625 = 25 and √324 = 18.

2. Multiply: 25 × 18 = 450.

3. Evaluate the squares: 9² = 81 and 13² = 169.

4. Substitute into the equation: 450 − 81 = √(?) + 169 + 100.

5. Simplify the left side: 450 − 81 = 369.

6. Isolate √(?): 369 − 169 − 100 = √(?), so √(?) = 100.

7. Square both sides to remove the root: (?) = 100² = 10000.

Cross-check by substituting (?) = 10000: √10000 = 100. The right side becomes 100 + 169 + 100 = 369. The left side is 25 × 18 − 81 = 450 − 81 = 369. Both sides equal 369, confirming the value.

Therefore, (?) = 10000.