Answer:
1. Find the prime factorization of 210
210 = 2 × 3 × 5 × 7
2. Find the prime factorization of 450
450 = 2 × 3 × 3 × 5 × 5
3. Multiply each factor the greater number of times it occurs in steps i) or ii) above to find the LCM:
LCM = 2 × 3 × 3 × 5 × 5 × 7
LCM = 3150