Question 902983
{{{16 = 24(1-e^(-t/2))}}} 
 {{{1-e^(-t/2)=2/3}}}
{{{-e^(-t/2)=-1/3}}}
{{{e^(-t/2)=1/3}}}
{{{-t/2=ln(1/3)}}}
{{{t=-2*ln(1/3)}}}