Take the 14.87% of phosphorus and convert it to grams giving you 14.87 grams of phosphorus. Then you divide 14.87 by the mass of phosphorus which is 30.97 grams then multiply it by one mole. Giving you 0.48 moles of phosphorus. Do the same with the Chlorine, 85.13/35.45 x 1 = 2.4. Take the smaller of he numbers and divide it into both numbers, 0.48/0.48=1 and 2.4/0.48= 5
Empirical formula is 1P 5Cl
