Question

x - y = 5,
x+2y=-1.
система

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Answer 1

{

x+2y=−1

x−y=5

{

x+2y=−1

x=5+y

(5+y)+2y=−1

3y=−6

y=−2

x=5−2

x=3

Answer 2

$\left \{ {{x-y=5} \atop {x+2y=-1}} \right.\\\left \{ {{x=5+y} \atop {x+2y=-1}} \right.\\(5+y)+2y = -1\\3y = -6\\y = -2\\x = 5 - 2\\x = 3$