When 155 ml of water at 26 c is mixed with 75 ml of water at 85 c, what is the final temperature? (assume that no heat is lost to the surroundings; d of water 1.00 g/ml.)

The assumpiton (no heat is lost to the surroundings) => all the heat lost by the hot water is gained by the cold water

Heat lost by the hot water, H1: m1*Ce*(T1 - To)

m1=155mL*1.00g/mL = 155g => H1 = Ce*155g*(85 -x)

Heat gained by the cold water, H2 = m2*Ce*(To-T2)

m2 = 75g => H2= Ce*75g*(x - 26)

H1 = H2 => 155 (85-x) = 75(x-26)

13175 - 175x = 75x - 1950

75x + 175x = 13175 + 1950

250x = 15125

x = 15125 / 250 = 60.5

the final temperature is 60.5 °C