How many grams (of mass m) of glucose are in 285 ml of a 5.50% (m/v) glucose solution?

The percentage of glucose given is m/v. This means that the given percentage of volume consists of mass.
In this solution, percentage of glucose is 5.5% m/v.
This means that 5.5% of the volume is the mass of glucose.
Given volume is 285 mL. 
Therefore mass of glucose is 5.50% of 285 mL = (5.5*285)/100
mass of glucose = 15.67 g