SOLUTION: Solve the system of equation by the substitution method x+y=20 5x+y=0

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Question 1102710: Solve the system of equation by the substitution method
x+y=20
5x+y=0
Answer by algebrahouse.com(1659) About Me  (Show Source):
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x + y = 20
5x + y = 0 ----> y = -5x {subtracted 5x from each side}

x - 5x = 20 {substituted -5x, in for y, into first equation}
-4x = 20 {combined like terms}
x = -5 {divided each side by -4}

x + y = 20 {first equation}
-5 + y = 20 {substituted -5, in for x, into first equation}
y = 25 {added 5 to each side}

x = -5 and y = 25

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