Which numbers are even numbers?
How can monsters split the flies? There are two monsters, Lisa and Oscar. They can split the flies only if there is an even quantity.
Even numbers are: 2, 4, 6, 8 and all the greater numbers that end with 0, 2, 4, 6, 8. All the numbers ending with 0, 2, 4, 6, 8 are even numbers.
The two monsters can divide the flies in half: there are 6 flies so Lisa and Oscar will have 3 flies each!