The second and seventh term of a G.P are 18 and 4374 respectively.

Find the common ration
Sum of the 4th and 8th terms
Sum of the first 10th terms

ar = 18

ar^6 = 4374
divide them:
r^5 243 = 3^5
so r = 3

now you can find a, and using your definitions all the other parts asked for