What mass of hot water at 70 degrees C must be added to 2000g of cold water at 5 degrees C to raise it's temperature to 20 degrees C?

Question

To be honest I really don't have any idea how to do this question. I would really appreciate help, thank you

Answer 1

well let's call the specific heat of water = k. It does not matter what it is
now the heat added to the cold = the heat taken from the hot

2000 k (20-5) = m k (70-20)
2000 (15) = m (50)

m = 2000 (15/50) grams

Answer 2

Thank you!!