Kathleen deposits $20 into her account that earns 2.5% interest that is compounded twice a year. how much money will kathleen have in her account in 30 years?

Present value, P = 20
compounding interest per 6 months, i  = 0.025/2 = 0.0125
Number of periods, n = 30*2 = 60 (half-years)

Future value in 30 years
=P(1+i)^n
=20(1.0125)^60
= $42.14