So, the multiples for 4 and 10 are...
4,8,12,16,20...
10,20,30,40,50...
So, basically LCM means least common multiple which just means that from the two numbers that you're given (4 & 10) there is one number that goes into both of them and is the smallest amount.
So for 4 and 10, the numbers that go into both of them are 20 and 40. out of both of these numbers 20 is the lowest, making it the LCM. Hopefully that helped, and if it didn't then I'm sorry. Good luck with the rest queen.