The sum will be:
sigma(i = 1 to infinity, 30*(2/5)^i)
->

Which is equal to 30/(3/5) = 50
Answer:
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Step-by-step explanation:
∠BDC=30, so ∠CBD + ∠BCD=180-30=150
ΔDBC is isosceles, so ∠CBD=∠BCD=half of 150=75
∠ABC=∠ABD-∠CBD=155-75=80
ΔABC is isosceles, so ∠ABC=∠ACB=80
∠BAC=180-80-80=20
I=PRT
I=interst
P=invested amount
R=rate in decimal
T=time in years
given
P=680
R=3.5%=0.035
T=6
I=680*0.035*6
I=142.8
that is interest
total is interest+principal=680+142.8=822.8
after 6 years, $822.80 is in the account
6/15 = 2/c
6/3 = 2, therefore you must divide 15 by 3 to get 5. c = 5
6/15 = 2/5