Răspuns :
[tex]\displaystyle\\a+b=s\implies \begin{cases} a=s-b \\ b=s-a \end{cases}.\\a-b=d\implies \begin{cases} a=b+d \\ b=a-d \end{cases}.\\[/tex]
[tex]\displaystyle\\a+b=s\implies \begin{cases} a=s-b \\ b=s-a \end{cases}.\\a-b=d\implies \begin{cases} a=b+d \\ b=a-d \end{cases}.\\[/tex]