Heat reaction question?

Question

I'm doing this chapter on heat reactions, enthalpies, etc. and I am absolutely confused. I've banged my head against the wall 21 times. I just don't understand it. Here's a question that is a good example of how all my other questions are. Could you not just give the answer, but show me how to do it? Thanks.

What is the final temperature, in degrees C, when 60.0 g of water at 80 degrees C is mixed with 40.0 g of water at 25 degrees C. The specific heat of water is 4.184 J/g x C.
a) 53 b) 58 c) 70 d) 35 e) 42

Thanks in advance

Answer 1

First the specific heat of water is not needed because both items mixed are water and would have the same specific heat so just use the weight.

so you have 60 * 80 + 40 * 25 = 100 * x where x is the new temperature in degrees C

If the items being mixed were different then use the specific heat of each item to calculate the number of joules in each item which will give the total number of joules in the combined item.