Answer
See the answer below.
Work Step by Step
There are $8\times 1/8=1$ $Ca^{2+}$ ions inside the lattice (one per vertex);
$6\times 1/2=3$ $O^{2-}$ ions in the lattice (one per face);
one $Ti^{4+}$ in the center of the lattice
the charges also cancel out: $+2+4+3\times-2=0$
