Answer :
[tex]if\ "i"\ is\ the\ imaginary\ unit:\sqrt{-1}=i\Rightarrow i^2=-1\\\\then\\\\\frac{5+5i}{2+i}=\frac{5+5i}{2+i}\cdot\frac{2-i}{2-i}=\frac{10-5i+10i+5i^2}{2^2-i^2}=\frac{10+5i-5}{4+1}=\frac{5+5i}{5}=\boxed{1+i}[/tex]
