if a patient should receive a medication at 15mg/kg/day in three equally divided doses what will be the approximate dose if the patient weighd 142lb?

142 lb x (1 kg/2.2 lb) = about 64 kg but you should do this more accurately.

(15 mg/kg) x 64 kg = about 960 mg/day
Divide that into three parts so 960 mg/3 = ? mg/each dose for 3 doses/day.