Question 1114124
{{{y=p*2^(x/20)}}}
y, population after x weeks
p, initial population



{{{80*2^(x/20)=1000}}}


{{{2^(x/20)=12.5}}}


{{{(x/20)log((2))=log((12.5))}}}


{{{x=20*log((12.5))/log((2))}}}


72 weeks and 6 days
If to the nearest day