\(10x+145=155155\)
\(10x=155010\)
\(x=15501\)
\(\left(x+1\right)+\left(x+4\right)+...+\left(x+28\right)=155155\)
\(=>\left(10x\right)+\frac{\left(28+1\right).10}{2}=155155\)
\(=>10x+\frac{290}{2}=155155\)
\(=>10x=155155-\frac{290}{2}=155155-145\)
\(=>10x=155010\)
\(=>x=\frac{155010}{10}=15510\)