Chemistry help?

Molar mass of Ca²⁺ = 40.08 g/mol = 40.08 mg/mmol

Mole ratio Ca²⁺ : EDTA = 1 : 1
No. of milli-moles of EDTA = (0.010 mmol/mL) × (8.1 mL) = 0.081 mmol
No. of milli-moles of Ca²⁺ in 10 mL of the solution = 0.081 mmol
No. of milli-moles of Ca²⁺ in 100 mL of the solution = (0.081 mmol) × (100/10) = 0.81 mmol
Mass of Ca²⁺ in 100 mL of the solution = (0.81 mmol) × (40.08 mg/mmol) = 32.5 mg