Answer:
Both are equal
Step-by-step explanation:
Mass of starting material i.e Aluminium is
grams
The weight of oxygen is

There are 4 atoms of aluminium and 3 atoms of oxygen
Thus, the total mass of starting material is
mass of one atom of aluminium
mass of one atom of oxygen

grams
Mass of new substance is also equal to
mass of one atom of aluminium
mass of one atom of oxygen

grams