What expression defines Sn?

Answer:
Sₙ=3(1/2^n)
Step-by-step explanation:
Notice that in the given series that each term is being multiplied by 1/2, which is our common ratio. 3/2 is the first term because 3*1/2=3/2, so the expression that defines Sₙ is Sₙ=3(1/2^n)