Answer
See answer below.
Work Step by Step
Number of moles of urea:
$95\ mg\div 60.06\ mg/mmol=1.58\ mmol$, same as the others from stoichiometry.
Mass of arginine:
$1.58\ mmol\times 174.20\ mg/mmol=275.2\ mg$
Mass of ornithine:
$1.58\ mmol\times 132.16\ mg/mmol=208.8\ mg$
