Question

A 32.3 g iron rod, initially at 22.4 ∘C, is submerged into an unknown mass of water at 62.9 ∘C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 59.4 ∘C.

Answer 1

I suppose you want to know the mass of H2O but you don't ask it directly.
Heat lost by Fe + heat gained by H2O = 0
Note: sph = specific heat

[mass Fe x sph Fe x (Tfinal-Tinitial)] + [mass H2O x sph H2O x (Tfinal-Tinitial)] = 0