Can you explain why Q1 = 3.5 and Q3 is 9 out of this dataset 0, 1, 3, 4, 6, 7, 7, 7, 8, 10, 12, 12.

My answers were:
Assuming median would be 7 (using numbers in positions 6 and 7 where 7+7/2 = 7)
Q1 dataset would be 0,1,3,4,6; Q1 = 3

Q2 dataset would be 7,8,10,12,12; Q3= 10

Thanks

The middle 50% would be from between 3 and 4 to between 8 and 10 (the middle 6 scores).

Q1 defines the lowest 25% (0, 1, 3), while Q3 defines the highest 25% (10, 12, 12).