Problem $5-5$ Calculating the Number of Periods $[$LO$4]$

Solve for the unknown number of years in each of the following: $($Do not round intermediate calculations and round your answers to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$

$\backslash$table$[[$Present Value,Years,Interest Rate,Future Value$],[$$$,8,\%,$$$,987],[470,,12,\%,1,704],[720,,18,\%,275,671],[17,500,,14,\%,303,827],[20,600,,,,]]$