Quinten and his friends ate \( \frac{6}{12} \) of the peach pie, which simplifies to \( \frac{1}{2} \).
Since they ate the same fraction of the cherry pie, we need to find \( \frac{1}{2} \) of the cherry pie. The cherry pie has 8 slices.
Calculating \( \frac{1}{2} \) of 8 slices: \[ \frac{1}{2} \times 8 = 4 \]
Thus, they ate 4 slices of the cherry pie.
The answer is 4.