Need assistance in finding the df within for ANOVA testing.

For the df within I subtracted 8 from 8, but that gives me 0 which cannot be right because I would end up getting a Divided by 0 error for the MS within and the F. Can someone please explain how I may solve this? All I need is assistance with that part and I can solve the rest. I appreciate anyone that helps.

1. Test the claim that the exam scores on the eight College Algebra exams are equal. Use alpha error .05. Conduct follow up tests if necessary. Interpret all results.
Exam: 1 2 3 4 5 6 7 8
n: 24 24 24 24 24 24 24 24
mean: 62.21 68.17 70.59 63.84 74.35 66.44 65.00 62.37

Source SS df MS F
Between 2417.52 7 345.36 Error
Within 38147.32 (0)? Error
Total 40564.84 (7) ?