Answer
$8.7$
Work Step by Step
Solve the given formula for $ t.$
$ A=Pe^{rt}\quad $ ... $/\div P $
$(A/P)=e^{rt}\quad $ ... $/\ln(...)$
$\ln(A/P)=rt\quad $ ... $/\div r $
$ t=\displaystyle \frac{\ln(A/P)}{r}$
Insert the values given in the table.
$ t=\displaystyle \frac{\ln(2)}{0.08}\approx $8.6643 (round to 1 dec. place)