Answer:
5.493
Step-by-step explanation:
Given expression
⇒
[tex]40+ 30 e^{-.2x} =50\\30e^{-.2x} =10\\x^{-.2} =\frac{1}{3}[/tex]
apply Log to the base e on both sides
this calculation would requires a calculator or log table
[tex]ln(e^{-0.2x} )=ln(1/3)\\-0.2x= -1.099\\x=5.493[/tex]
