Why is x8 and x2 is x6 and not x4?

To divide indices you subtract, hust like to multiply you add. eg 5 to the sixth divide by 5 to the fourth is five to the (6 - 4) ie 5 squared ie 25.

Check it : 5 to the sixth = 5 x 5 x 5 x 5 x 5 x 5; 5 to the fourth = 5 x 5 x 5 x 5;

To divide 5 x 5 x 5 x 5 cancels out leaving 5 x 5.