Answer:
The answer to your question is 105
Step-by-step explanation:
To get the least common factor dividing both numbers by the prime numbers starting from 2.
But these numbers are not multiples of 2, try 3
21 105 3
These numbers are not multiples of 3 let's try 5
7 35 5
These numbers are multiples of 7 7 7 7
1 1
The LCM is the product of the prime numbers = 3 x 5 x 7 = 105
