\(\left(y+1\right)+\left(Y+3\right)+...+\left(y+99\right)=2550\)
\(\left(y+y+..+y\right)+\left(1+3+5+...+99\right)\)
\(50y+\frac{\left(99+1\right).50}{2}=2550\)
\(50y+2500=2550\)
\(\Rightarrow50y=50\)
\(\Rightarrow y=50:50=1\)
\(\Rightarrow y+y+...+y+1+3+...+99=2550\Rightarrow50y+\frac{\left(99+1\right)\cdot50}{2}=2550\)
\(\Rightarrow50y+2500=2550\Rightarrow50y=50\Rightarrow y=1\)