Adoctor has ordered that a patient be given 15g of glucose, which is available in a concentration of 75.00g glucose/1000.0 ml of solution. what volume of solution should be given to the patient?

I would start by converting g/mL to g/L
75.00g/1000.0mL = 75.00g/L
Stoichiometrically, flip 75 onto the bottom so that grams cancel out and we are left with the number of L required. 
(L/75.00g)(15g) -> this is essentially dividing 15g by 75g, which cancels the unit g, leaving us with 0.2L. If the question requires an answer in mL, just multiple the number of L by 1000. 
The patient requires 200mL of glucose solution to receive his 15g of glucose. 

Given the concentration (C) in mass per volume, the volume (V) of the solution is obtained by dividing the mass (m) by this concentration (C). So, from the given,
                         V = C / m   = (15 g) / (75 g / 1000 mL)
The numerical value of V is equal to 200 mL. 

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