Answer is: 34.2 mL sodium phosphate solution is necessary to completely react.
Chemical reaction: 2Na₃PO₄ + 3CuCl₂ → 6NaCl + Cu₃(PO₄)₂.
n(CuCl₂) = c(CuCl₂) · V(CuCl₂).
n(CuCl₂) = 0.103 M · 0.0907 L.
n(CuCl₂) = 0.00934 mol.
From chemical reaction: n(CuCl₂) : n(Na₃PO₄) = 3 : 2.
n(Na₃PO₄) = 2 · 0.00934 mol ÷ 3.
n(Na₃PO₄) = 0.00622 mol.
V(Na₃PO₄) = n(Na₃PO₄) ÷ c(Na₃PO₄).
V(Na₃PO₄) = 0.00622 mol ÷ 0.182 M.
V(Na₃PO₄) = 0.0342 L · 1000 mL/L = 34.2 mL.
