Respuesta :
Step-by-step explanation:
my workings and answers is in the image above

Answer:
There is another approach to this problem that
might be more in line with what you are studying ..... NOTE: the first answer is correct.
Step-by-step explanation:
1 = 2[tex]x^{4}[/tex]
1/2 = [tex]x^{4}[/tex]
ln(1/2) = 4 ln(x)
ln(1/2)/4 = ln(x)
x = [tex]e^{-0.1732}[/tex]
x = .8408
~~~~~~~~~~~~~~~~
model : 840[tex](0.8408)^{t}[/tex]
~~~~~~~~~~~~~~~~~
(.03* 840) = 840[tex](0.8408)^{t}[/tex]
(.25.2) = 840[tex](0.8408)^{t}[/tex]
.03 = [tex](0.8408)^{t}[/tex]
ln(.03 )=ln( [tex](0.8408)^{t}[/tex])
t = ln(.03 )/ln(0.8408 )
t = 20.22