The question is: When you take a bath, how many kilograms of hot water(49.0 Degrees Celcius) must you mix with cold water(13.0 Degrees Celcius) so that the temperature of the bath is 36.0 Degrees Celcius. The total mass of water(hot + cold) is 191kg. Ignore any heat flow between the water and the external surroundings. As far as i know Q=mL, where m is the mass of the cold water, Q=cm(change in T), where T is the higher temperature minus the lower eauilibrium temperature. And that the equilibrium temperature is 36. But i don't understand how to deal with this question if the temperature given is for both hot and cold water. If i had one of those, the question would have been easy.