What will come in place of question mark (?) in the following question? 38% of…

Concept: To find an unknown percentage-based quantity, first evaluate the percentage of the known number using the rule x% of N = (x × N) / 100. Then convert a percentage of the unknown, "y% of ?", into an algebraic term (y/100) × ? and solve the resulting linear equation for the unknown.

1. Compute 38% of 4500 = (38 × 4500) / 100 = 1710.

2. Write the equation using this value: 1710 - 25% of ? = 1640.

3. Isolate the percentage term: 25% of ? = 1710 - 1640 = 70.

4. Convert 25% of ? to (?/4) since 25% = 1/4, so ?/4 = 70.

5. Solve for ?: ? = 70 × 4 = 280.

Cross-check: Substituting ? = 280 back into the original equation gives 38% of 4500 - 25% of 280 = 1710 - 70 = 1640, which matches the given equation, confirming 280 is correct.