To find the correct dosage of naproxen sodium for an adolescent weighing 85 lbs using Clark's rule, we follow these steps: First, convert the weight from pounds to kilograms by dividing by 2.2. For an 85 lb adolescent, this is 85 lbs ÷ 2.2 = 38.6 kg. Next, calculate the child's dosage fraction by dividing the patient's weight in kilograms by the average adult weight of 70 kg. This gives us 38.6 kg ÷ 70 kg = 0.5514. Finally, multiply the adult dosage (220 mg) by this fraction to find the correct dosage for the adolescent: 220 mg × 0.5514 = 124.6667 mg, which rounds to approximately 125 mg. Therefore, the correct dosage of naproxen sodium for the adolescent is 125 mg.