heat lost by Cu + heat gained by water = 0
mass x specific heat Cu x delta T = q Cu.
mass x specific heat H2O x delta T = q H2O.
delta T is Tfinal-Tinitial. You are given the initial T for both Cu and water, Tf is the unknown for which you solve. You must look up the specific heats of Cu and H2O.
I have assumed in the above that the final T of the water is NOT greater than 100. If it is another approach must be used.
I'm a bit confused so is this the right way to set up the problem
heat lost by Cu+heat gained by water=0
5.26g(.385)(Tf-258C)+125g(4.18)(Tf-21C)=0 then you solve for Tf?
Yes, you have it set up correctly. Solve for Tfinal.