Question

What is the the formula for the compound cobalt(II) phosphate.

Answer 1

Cobalt(II) has a charge of 2+
Phosphate has a charge of 3-

Because it's an ionic compound, you will need to take the charge and make them subscripts.

The formula for cobalt(II) phosphate is Co₃(PO₄)₂

Your answer is
$\sf{Co_3(PO_4)_2}$