The equivalent mass of iron in Fe₂O₃ would be:

Equivalent weight definition: weight of substance required to combine or displace 8 grams oxygen or 1 gram hydrogen.

One electron transfer is enough to displace and combine with hydrogen or oxygen

In Fe₂​O₃​, the oxidation state of Fe is +3.

It means one third on Fe mole is enough to combine with 8 grams of O₂​ 

Therefore, the equivalent weight of iron in Fe₂​O₃​ = $\frac{55.8}{3}$​ = 18.6 g