[tex]\it\left. \begin{aligned} \it a+b=345 \Rightarrow a=345-b\\ \\ \it a-b=145 \Rightarrow a=145+b\end{aligned}\right\} \Rightarrow 145+b=345-b \Rightarrow b+b=345-145 \Rightarrow \\ \\ \\ \Rightarrow 2b=200|_{:2} \Rightarrow b=100\\ \\ \\ a=145+b=145+100=245[/tex]
