Answer:
A. t(x) = 450 - 0.06x
Step-by-step explanation:
The layer which is originally 450 m thick is decreasing by 0.06 m.
450 - 0.06
... per day. x represents days.
0.06x
So,
450 - 0.06x
They all 3 have no solution!
the equation for compound interest is

we will see if it doubles or not
if t=1, we get A=P(1+r)
if t=2, we get A=P(1+r)^2
2(P(1+r))=P(1+r)^2 ?
2(1+r)=(1+r)^2 ?
2+r=r^2+2r+1
etc
when r=-1.618 or 0.618, then it doubles, but not when r is different things
not always
so no, it does not always double the amount of interest earned
-1.5 would be the inverse