Identify the half reaction as oxidation or reduction.

sn > sn2+ + 2e¯
cl2 + 2e¯ > 2cl¯

OILRIG:
Oxidation is loss (of electrons)
Reduction is gain (of electrons)
so...
The first one is an oxidation half-equation as the Sn loses electrons;
The second one is a reduction half-equation as the Cl₂ gains electrons

The balanced equation is

4Fe(s) +  3O2(g)  ---> 2Fe2O3(s)

here four moles of Fe will react with O2 to give 2 moles of Fe2O3

mass of Fe reacted = 33.4 grams

moles of Fe reacted = mass of Fe / atomic mass of Fe

moles of Fe reacted = 33.4 / 55.8 = 0.599 moles

moles of Fe2O3 formed = 0.5 X 0.599 = 0.2995 moles

so mass of Fe2O3 formed = moles X molar mass = 0.2995 X 159.69 = 47.83 g