I tried I got the first one I think but i is equal to the square root of -1 so I'm honestly not too sure if it's fully simplified. As for the others I, don't have much of a clue at all.
7 . 9i^26 - 14i^27 / i^7 = 9i^19 - 14i^20
8. 3 - i / 3 + 2i
9. -i (-3i^3 + 4i^2 - 2i + 5) = 3i^4 - 4i^3 + 2i^2 - 5i
10. 2√(-27) - 4√(-75)