SOLUTION: The sum of three numbers is 20. The first number is the sum of the second and third. The third number is three times the first. Find the numbers

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Question 535464: The sum of three numbers is 20. The first number is the sum of the second and third. The third number is three times the first. Find the numbers
Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
x + y + z = 20
.
x = y + z
.
z = 3x
.
substitute z = 3x
.
x = y + 3z
-2x = y
.
substitute z = 3x and y = -2x
.
x + (-2x) + 3x = 20
.
2x = 20
.
x = 10
.
z = 3x = 30
.
y = -2x = -20
.
Checking...
x + y + z = 10 -20 + 30 = 20
.
Answer: The three numbers are -20, 10, and 30.
.
Done.