SOLUTION: Three numbers add up t0 140. The second number is twice the first, and the third number is twice the second. What are the three numbers?

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Question 272875: Three numbers add up t0 140. The second number is twice the first, and the third number is twice the second. What are the three numbers?
Answer by JBarnum(2146) About Me  (Show Source):
You can put this solution on YOUR website!
xyz are our numbers
the first number is x
the second number is y
the third number is z
x%2By%2Bz=140
y=2x "The second number is twice the first"
z=2y "third number is twice the second"
_________________________
Solve for x by using substitution
x%2B2x%2B%282%282x%29%29=140 multiply
x%2B2x%2B4x=140 add
7x=140 divide
x=20
___________
solve the other 2 equations
y=2x
y=2%2820%29
y=40
___________
z=2y
z=2%2840%29
z=80
20,40,80 are the 3 numbers in order.