Answer:
Population after 
Step-by-step explanation:
If
is the initial amount,
is the annual rate of decrease then after
years the remaining amount
will be given by

Here 
Answer:
a=4 n=25
Step-by-step explanation:
5a+5=n
(a+n)-4+25
a+n=29
5(4)+5=n
20+5=25
Well you can find the solution using the calculator
The answers:
27
33.9
18.97
34.85