Answer:
3 Ca
3 S
12 O
Step-by-step explanation:
You have 3 moles of Ca(SO4)
Therefore you multiply the subscript of each atom of the compound by 3.
Ca and S have a understood subscript of 1 so there are three of each.
There are 4 oxygen atoms in one mole of CaSO4 so in 3 moles there would be 4*3 so 12