Hello!
To write this equation we will use c to represent the total cost, and g to represent however many games you download.
c=12.49+0.99g
The constant rate is 12.49, that will never increase or change in our equation.
Depending on how many games you download, that will be the rate that affects our total cost.
If you only purchase one game, you only spend $13.48. Where as if you buy 10 games, you spend $22.39.