How many moles of Ca2+ ions are there in 0.45 moles of CaTiO3?
How many eggs in half a dozen eggs?
You have 0.45 mol perovskite. In each mole of perovskite there are 3 moles of oxygen atoms, 1 mol titanium, and 1 mol of calcium.
So, given this 1:1 molar equivalence, how many moles of calcium ions are there in 0.45 moles?