The answer is 28 years
At = A0 * e^(-k * t)
At = 12 g
A0 = 15 g
k = 7.9 × 10^-3 = 0.0079
t = ?
12 = 15 * e^(-0.0079 * t)
12/15 = e^(-0.0079 * t)
0.8 = e^(-0.0079 * t)
Logarithm both sides (because ln(e) = 1:
ln(0.8) = ln(e^(-0.0079 * t))
ln(0.8) = (-0.0079 * t) * ln(e)
-0.223 = -0.0079 * t
t = -0.223 / -0.0079
t = 28.23
t ≈ 28 years
Answer:

Step-by-step explanation:
The equation of line in the form .
y = mx + c
Where m is the slope and c is the y- intercept .
As given
The lines y=3x-1 and y=ax+2 are perpendicular .
Here 3 is slope for equation of line y=3x-1 and a is slope for equation of line
y=ax+2 .
Now by using properties of the perpendicular lines property .
When two lines are perpendicular than slope of one line is negative reciprocal of the other line .
Thus

Therefore 
Answer:
D 714
Step-by-step explanation:
210 times 3.40
is 714
This is so hard im so sry i dont get it