How much water at 65 C must be mixed with 600 gm of water at 25 C in a 55 gr can specific heat .1, if the temperature of the mixture is to be 31 C?

The initial heat of the water and can is

600*Cw*25 + 55*0.1*25 + x*Cw*65

The final heat of the water and can is

(600+x)*Cw*31 + 55*0.1*31

Set the inital and final heat equal to each other, and solve for x; You will have to look up the specific heat of water (Cw), it should be in the same units as that listed for the specific heat of the can