While this may look like it's a lot to keep track of, its not too bad. We have 7 copies of (-8) in total. The 7 copies due to the exponent of 7. Nice work on getting the correct answer for the second part.
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A further detailed breakdown:
(-8)^3 is the same as (-8)(-8)(-8) so we have three copies here
(-8)^4 is the same as (-8)(-8)(-8)(-8) and we have four copies
Overall, we have 3+4 = 7 copies total.