let the two numbers be: x y
x + y = 8
x - y = 12
Isolate the x in x + y = 8. Subtract y from both sides
x + y (-y) = 8 (-y)
x = 8 - y
Plug in 8 - y for x in the other equation
x - y = 12
(8 - y) - y = 12
Simplify
8 -2y = 12
Isolate the y. Subtract 8 from both sides, and then divide by -2
8 (-8) - 2y = 12 (-8)
-2y = 4
-2y/-2 = 4/-2
y = -2
Plug in -2 for y in one of the equations
x + y = 8
x + (-2) = 8
Simplify. Isolate the x. Add 2 to both sides
x - 2 (+2) = 8 (+2)
x = 10
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x = 10, y = -2 is your answer
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hope this helps
