Answer:
There are 6 seating orders possible.
Step-by-step explanation:
1. Andrew, Marco, Kenjo
2. Marco, Kenjo, Andrew
3. Kenjo, Marco, Andrew
4. Kenjo, Andrew, Marco
5. Andrew, Kenjo, Marco
6. Marco, Andrew, Kenjo
6/15 + 10/15 = 16/15 = 1 1/15
6/15 - 10/15 = -4/15