Answer
Please see the work below.
Work Step by Step
We know that according to law of conservation of energy
$Q_{water}=-Q_{iron}$
$\implies m_{water} c_{water}\Delta T_{water}=-m_{iron}c_{iron}\Delta T_{iron}$
We plug in the known values to obtain:
$(15)(4184)(T_f-20)=(1.1)(447)(550-T_f)$
$T_f=24^{\circ}C$
