You have to pull apart 16 and 28 so you have their end prime factors Which are:
16: 2 2 2 2 28: 2 7 2
If the same factor occurs more than once in both numbers, you multiply the factor with the greatest number of times it occurs multiply them to 7 to get the lcm with prime factorisation
2x2x2x2x7 =112 ❤️❤️ if this doesn’t make sense message me I really don’t mind