Explanation:
It should be in this order from oldest to youngest: 2,1,5,7,9,3,4,8,6.
Since we know 2 is the oldest and once each organism goes extinct it stops being in any samples, we can start at 2 and go through the samples to see where that fossil shows up again and when we find the next sample its in, we pay attention to any new fossils that show up and move onto the next sample with the second fossil in it and so on.
