First, you have to write down the equation from glucose, C₆H₁₂O₆, to ethanol, C₂H₅OH.
C₆H₁₂O₆ --> 2 C₂H₅OH + CO₂
So, the ratio for glucose to ethanol is 1:2. The solution is as follows:
Mass of glucose required = (475 g)(0.87)(1mol/46.07 g ethanol)(1mol gluose/2 mol ethanol)(180.2 g/mol glucose)
Mass of glucose required = 808.2 g