A simple exercise:
The circle to the right represents a pie. Your goal is to cut this pie into 8 pieces using only three lines. Have at it!.
Solution (swipe text below):
The trick to figuring this out is thinking three-dimensionally. First, quarter the circle with two lines (or slices, if you will). Then remember that there is a third dimension that cannot be seen in the picture. If you were to cut along that axis, you would have 8 pieces of pie!