Concept: A percentage of the total income is given, so find the whole when the part and percentage are known.Explanation:Let the man's net monthly income be M.He donates 10% of M, which is N4,500.This means 10%×M=4500.Write 10% as 10010, so 10010M=4500.Multiply both sides by 10100 to solve for M.M=4500×10100.10100=10, so M=4500×10.M=45000.Answer: N45,000. Option B.