Answer
$N=1500~deers$
Work Step by Step
Find the horizontal asymptote.
$N=\frac{20(5+3t)}{1+0.04t}=\frac{100+60t}{1+0.04t}$
The denominator and numerator have the same degree. The horizontal asymptote is the ratio of the leading coefficients:
$N=\frac{15}{0.04}=1500$