maura2mconroy0547
maura2mconroy0547 maura2mconroy0547
  • 02-03-2017
  • Mathematics
contestada

the sum of three numbers is twenty. the second number is four times the first and the sum of the first and third is eight. what are the three numbers?

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baabaagreysheep
baabaagreysheep baabaagreysheep
  • 02-03-2017
Let's call the three numbers x, y, and z. 


The numbers are 3, 12, and 5.
x + y + z = 20
y = 4x
x + z = 8
We can rewrite the first equation because y is 4x, so 
x + 4x + z = 20
5x + z = 20
And now we can use simultaneous equation rules to solve

5x + z = 20
x + z = 8

5x + z = 20
5x + 5z = 40
(subtract)
-4z + -20
÷ -4
z = 5

x + z = 8
x + 5 = 8
x = 3

y = 4x
y = 4 × 3
y = 12

I hope this helps!
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