What is the final temperature after thermal equilibrium is reached

A 170 g sample of water with a temperature if 29◦C is added to 300 g water at 85◦C in an insulated container.

Some discussion and sample problems:

http://www.chemteam.info/Thermochem/Mixi…

For your problem:

(170 g) (x - 29) (4.184) = (300) (85 - x) (4.184)

The 4.184 values cancel. The 'x' is the equilibrium temperature. Solve for it.