From the balanced equation: 
4mol Fe will produce 2mol Fe2O3 
Molar mass Fe = 55.847g/mol 
16.7gFe = 16.7/55.847 = 0.3mol Fe 
This will produce 0.15mol Fe2O3 
Molar mass Fe2O3 = 159.6887 g/mol 
0.15mol = 159.6887*0.15 = 23.95g Fe2O3 produced
Hope this helps