molarity = moles of solute/liters of solution
We know the moles of solute: 0.875 moles of glucose. We can easily determine the liters of solution by using the mass of water given (1.5 kg) and the density of water (approximately 1 kg/L): they're, for all intents and purposes, equal (the approximation isn't large enough to be appreciable here, nor would the volume of the solution appreciably change since the solute is a solid that will dissolve into the solvent). So, we have 1.5 L of solution.
Now, we plug in what we have:
molarity = 0.875 moles of glucose/1.5 L of solution = 0.58 M glucose
The answer is provided to two significant figures since we're given the mass of water to two significant figures.