Question

Asoma de dois números é 50 e a diferença é 30. Quais são esses números.

Answer 1

$\begin{cases}x+y=50\\ x-y=30\end{cases}\\\\\\x+y=50\to~~x=-y+50\\\\\\ x-y=30\to~~ -y+50-y=30\to~~-y-y=30-50\to\\\\ -2y=-20~(-1)\to~~2y=20\to~~y= \dfrac{20}{2} \to~~\boxed{y=10}\\\\\\x=-y+50\to~~x=-10+50\to~~\boxed{x=40}\\\\\\\\ \large\boxed{\boxed{S=\{40~;~10\}}}$