(B) 4 and 5
4 and 5 are consecutive numbers and when you add both of them (sum) you get 9.
Once you get 9, it says 1/3 of the sum of the two consecutive numbers.
So we would do 9 divided by 3 which then we would get 3.
It also says the number is one less than the smaller number (which is 4 in this case as 4 is smaller than 5).
3 is one number smaller than 4 and is therefore the answer.
