Anew video game is expected to sell 120 copies the first hour at a local game store. after that, the sales will follow the function s(x) = 15(x − 1) where x is the number of hours. what is the function that shows total sales, including the first hour?

The first hour, they sell 102 copies.  
So the function starts with : s(x) = 102 + ( I put a + after 102 because we know that there are following sales after the first hour ). 

Then, the sales are s(x) = 11 (x-1). 
So this is the second part of your function. 

102 + 11 (x-1)