Answer: 765
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Work Shown:
a = 3 is the first term
r = 2 is the common ratio
Sn = a*(1-r^n)/(1-r) ... sum of the first n terms
S8 = 3*(1-2^8)/(1-2) ... sum of the first 8 terms
S8 = 3*(-255)/(-1)
S8 = 765
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We can generate the first 8 terms to get 3, 6, 12, 24, 48, 96, 192, 384. Each new term is found by multiplying the previous one by 2.
Then add them up to get 3+6+12+24+48+96+192+384 = 765. We get the same result.
