Need help solving this math class work I don’t understand it

Given:
[tex]\frac{2+i}{1-2i}[/tex][tex]\frac{2+i}{1-2i}=\frac{2+i}{1-2i}\times\frac{1+2i}{1+2i}[/tex][tex]\frac{2+i}{1-2i}=\frac{2+4i+i-2}{1+4}[/tex][tex]\frac{2+i}{1-2i}=\frac{5i}{5}[/tex][tex]\frac{2+i}{1-2i}=i[/tex]