if you have 4350 gallons of 80 degree water and add 60 gallons of 125 degree water how warm would the water temp get.

Answer 1

assuming you mix them, treat it as a general mixture problem, where the total "energy" must add up:

4350*80 + 60*125 = (4350+60)x
x = 80.6

Not much of a change, but then 60 gallons is pretty small compared to 4350 gallons.