In every balanced chemical equation, each side of the equation has the same number of atoms of reactants and products.
For example, let's take this chemical equation.
This is the chemical equation for carbon monoxide reacting with dihydrogen to form octane and water.
8 CO + 17 H2 → C8H18 + 8 H2O
On this side, we have 8 carbon monoxide atoms and 34 dihydrogen atoms.
On the other side, we have 8 carbon atoms and 18 hydrogen atoms + 16 hydrogen atoms.
Therefore, even though the coefficients are different there is still an equal number of atoms on each side.
8 Carbon Monoxide , 34 Dihydrogen = 8 Carbon Monoxide + 34 Dihydrogen