80.87 °C
Change in Temp of metal = (C of water *mass of water* Change in temp of water)/(C of metal*mass of metal)
That is;
Change of temp. of metal
  = [(4186 J/kg*°C)×(0.15kg)×(25°C-21°C)/[(899 j/kg*C)×(0.050kg)
   = 55.87 °C
The change in temp of the metal is -55.87 °C  as the metal cools down
Therefore;
Change in temperature = Final Temperature-Initial Temperature Initial                    Temperature = Final Temp.-Change in Temp
           =25 °C- (-55.87 °C)
            = 80.87 °C