NaPO4 + KOH -> KPO4 + NaOH
already balance
Do this has extra pictures/examples so I can help?
Answer: 
Explanation:
Firstly, we have to find the Molecular mass of potassium oxide (
):
atomic mass: 39 u
atomic mass: 16 u
molecular mass: 
This means that in 1 mole of
there are
and we need to find how many moles there are in
:
1 mole of
-----
of 
-----
of 

This is the quantity of moles in 73.9 g of potassium oxide
Now we can calculate the number of atoms in 73.9 g of potassium oxide by the following relation:

Where:
is the number of atoms in 73.9g of potassium oxide
is the Avogadro's number, which is determined by the number of particles (or atoms) in a mole.
Then:

This is the quantity of atoms in 73.9g of potassium oxide