Question

(2x+2y=10)+(-x+y=1)

Answer 1

$\bf \begin{cases} 2x+2y=10\\ -x+y=1 \end{cases}\\\\ -------------------------------\\\\ -x+y=1\implies y=1+x\impliedby \textit{let's plug that in the first equation} \\\\\\ 2x+2(\stackrel{y}{1+x})=10\implies 2x+2+2x=10\implies 4x=8 \\\\\\ x=\cfrac{8}{4}\implies \boxed{x=2}\impliedby \textit{let's plug that in the second one} \\\\\\ -(\stackrel{x}{2})+y=1\implies \boxed{y=3}$