\(\left(x+3\right)+\left(x+5\right)+\left(x+7\right)+...+\left(x+2011\right)=1005.3005\)
\(\Rightarrow\left(x+x+x+...+x\right)+\left(3+5+7+...+2011\right)=1005.3005\)
( 1005 số x )
\(\Rightarrow1005x+1012035=1005.3005\)
\(\Rightarrow1005\left(x+1007\right)=1005.3005\)
\(\Rightarrow x+1007=3005\)
\(\Rightarrow x=1998\)
Vậy x = 1998