9 apples per basket
Peter is making 8 identical fruit baskets. If the baskets are identical, that means they all have the same amount of fruit in them. If I know how many apples were used, then I can divide that by the total number of baskets (8) to find out how many apples were used per basket.
12 oranges were used per basket. There were 8 baskets. 12 x 8 = 96, so 96 oranges were used in total.
168 - 96 = 72
There were 72 apples used in total.
There were the same amount of apples in each of the 8 fruit baskets. 72/8 = 9, which means that there were 9 apples per fruit basket.
