Hello, this is a practice problem for a class I'm struggling with. The professor isn't much help, I'd really appreciate if someone here can answer this and break it down so I can follow the logic and see where I'm going wrong with these problems.

Find the sum of the rst 30 terms of a geometric sequence whose third term is 33 = 5.61 and whose eighth term is as = 15.19. Round your answer to the nearest whole number