Given :
Loan = $800
pay back = $920
Time = 5 years
Assume a simple interest
so,
[tex]\begin{gathered} A=P+I \\ I=P\cdot r\cdot t \\ A=P(1+r\cdot t) \end{gathered}[/tex][tex]\begin{gathered} P=800 \\ A=920 \\ t=5 \\ 920=800\cdot(1+5r) \\ 1+5r=\frac{920}{800}=1.15 \\ \\ 5r=1.15-1=0.15 \\ \\ r=\frac{0.15}{5}=0.03 \\ \end{gathered}[/tex]So, the annual interest = 0.03