Answer:
D. 21/2
Step-by-step explanation:
We simply have to evaluate the first three terms based on the progression's formula:
t= 1, the first term is 8, as we see:
t=2, the second term is 2, as we see:
t=3, the third term is 1/2, as we see:
The sum of the first 3 terms is then: 8 + 2 + 1/2 = 10 1/2
Among the answer choices, D. 21/2, which is 10 1/2.