can anybody here help me on this problem.... i've been trying to solve them with the use of the formula of geometric sequence and geometric series. but i could not make it to the answer.

Given: 1. S sub 5 = 31/4 ; r = 1/2 ; what is first term?

2. S sub n = 94.5 ; r = 1/2 ; a sub n = 3/2 ; what is n?

Thank you so much