The rat population in a major metropolitan city is given by the formula n(t)=51e^0.035t where t is measured in

years since 1991 and n(t) is measured in millions

What was the actual rat population in 1991 ?(not in millions)


What is the rat population going to be in the year 2002 ?

NOT in millions??? I'm not sure what you mean. I think you want:
n(0) = 51,000,000

2002 - 1991 = 11
11×.035 = .385
e^.385=1.469614321...
51×1.469etc. = about 74,950,330 rats, give or take a nest or two.

51 million rats in 1991.
Approximately 74,950,330.4 rats in 2002

All you need to do is put the function into a calculator. For 1991, it's been 0 years since 1991, so t = 0. 51e^(0.035*0) = 51. Do the exact same thing for 2002. It's been 11 years, so t = 11.