How do you solve $x+y=3$ and $x-y=1$ ?

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Answer 1 · 2015-08-01T23:05:17

Add the two equations together to get $2x=4$ hence $x=2$
Subtract the two equations to get $2y=2$ hence $y=1$

Add the two equations to find:

$2x = (x + color(red)(cancel(color(black)(y))))+(x-color(red)(cancel(color(black)(y)))) = 3 + 1 = 4$

Divide both ends by $2$ to get $x=2$

Subtract the two equations to find:

$2y = (color(red)(cancel(color(black)(x))) + y) - (color(red)(cancel(color(black)(x))) - y) = 3 - 1 = 2$

Divide both ends by $2$ to get $y = 1$

How do you solve x+y=3x+y=3 and x-y=1x-y=1?