First, let's find the total cost of all the apples:
[tex]8+(0.6\cdot15)=17[/tex]Now, we divide this by the total amount of apples bought. In our case, we know that there were 10 Granny Smith apples and 15 Golden Delicious, for a total of 25 apples.
[tex]\frac{17}{25}\rightarrow0.68[/tex]Therfore, we can conclude that the average cost per apple was $0.68