The answer is D. t = 9 log_5(43.25).
The image shows the following equation:
8*5^{-t/9}=346
To solve this equation, we can divide both sides by 8:
5^{-t/9}=43.25
Next, we can take the logarithm of both sides (base 5):
-t/9 = log_5(43.25)
Multiplying both sides by -9, we get the solution:
t = 9 log_5(43.25)
Therefore, the answer is D. t = 9 log_5(43.25).