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Answer:
D. 16.8 years
Step-by-step explanation:
The multiplier each year is 1-3% = 0.97, so the multiplier after x years is 0.97^x. You want to know the value of x when that multiplier is 60%, or 0.60.
0.97^x = 0.60
x·log(0.97) = log(0.60) . . . . . . take logarithms
x = log(0.60)/log(0.97) ≈ 16.8
At the given rate, it will be 16.8 years before 60% of the species remains.