Playing With Numbers

If $$n$$ represents an odd integer, which of the following must be even integers?
$$2n,3n,3n+1,3n-5,4n+1$$
How many multiples of $$3$$ are between $$23$$ and $$82$$?
The largest integer that divides product of any four consecutive integers is
If $$k$$ represents an integer, which of the following must be even integers?
$$2k,2k+6,\cfrac { 8k }{ 4 } ,3k+5,2k-1$$
Perform the indicated operations and simplify your answers to simplest form.
$$\cfrac{2}{15}+\cfrac{2}{3}=$$