To find the cost of each Macintosh apple, we can start by calculating the total cost of the Granny Smith apples.
The cost of 6 Granny Smith apples at $1.35 each is: \[ 6 \times 1.35 = 8.10 \]
Dahlia bought 6 Macintosh apples, and the total cost for both types of apples is $15. To find the total cost of the Macintosh apples, we can subtract the cost of the Granny Smith apples from the total cost: \[ 15 - 8.10 = 6.90 \]
Now that we know the total cost for 6 Macintosh apples is $6.90, we can find the cost of each Macintosh apple by dividing the total cost by the number of apples: \[ \frac{6.90}{6} = 1.15 \]
Thus, the cost of each Macintosh apple is $1.15.