Hi Jeon A
For
A(t)=P0(1+ r/n)nt
You just need to assign your values and plug them into the formula
A = Balance after 3 years
P0 = Initial investment $5000
r = your rate written as a decimal 0.025
n = number of compounding periods, yours is quarterly so you have 4
t = number of years
So you have
A(t) = 5000( 1 + (0.025/4))4*3
A(t) = 5000(1 + 0.00625)12
A(t) = 5000(1.00625)12
A(t) = 5000(1.0776) = 5388 to the nearest dollar.
You can check this by calculating the interest then adding it to the principal
C = P((1+ r)12 - 1)
C = Your total compounded interest
P = Your starting Principal
r = interest per period = 0.025/4 because your have quarterly compounding periods
n = total number of periods = 3years x 4 periods so in three years you have a total 12 periods
C = P((1+ r)12 - 1) =5000((1+.025/4)12 - 1) = 388 to the nearest dollar
C = 5000((1.00625)12 - 1))
C = 5000(1.0776 -1)
C = 5000(.0776) = 388
P + C = A = 5000 + 388 = 5388.
While these may not be the exact equations referred to in your text, you can look the many forms on the internet. I hope this helps