How many grams of calcium phosphate are required to give 30 grams of phosphorus

Convert the grams of phosphorus given to moles (by dividing by the molecular weight of P4). Do a mole ratio between the number of moles of phosphorous, and the number of moles of the target, which is calcium phosphate (1 mole P4 per 2 moles calcium phosphate). Then multiply by the molecular weight of calcium phosphate.