Answer:
9990 years
Step-by-step explanation:
The exponential function with given values filled in can be solved for the unknown using logarithms.
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Q(t) = 12 = 36e^(-0.00011t)
1/3 = e^(-0.00011t) . . . . . . divide by 36
ln(1/3) = -0.00011t . . . . . . take natural logs
t = ln(1/3)/(-0.00011) . . . . divide by the coefficient of t
t ≈ 9990 . . . years
6000 - 1800 = 4200
4200/4 = 1050
so she donated 25% to charity
Answer:
Step-by-step explanation:
12x −3y=36 ⇔ 3y = 12x - 36
y = 4x - 12
y = 0 ⇔ 4x - 12 = 0 ⇔ 4x = 12 ⇔ x = 12/4 = 3
So (0 ; - 12) and (3 ; 0)