SOLUTION: the average of three number is 39.if the first number is twice the second and the second is four times the third,find the numbers

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Question 697884: the average of three number is 39.if the first number is twice the second and the second is four times the third,find the numbers
Answer by Stitch(470) About Me  (Show Source):
You can put this solution on YOUR website!
Equation 1:A+=+2B
Equation 2:B+=+4C
Equation 3:%28A%2BB%2BC%29%2F3+=+39
Since B = 4C and A = 2B; A = 4C*2
So A = 8C
Rewrite equation 3 in terms of C
Equation 3:%28A%2BB%2BC%29%2F3+=+39
%288C+%2B+4C+%2B+C%29+%2F+3+=+39
Multiply both sides by 3
8C+%2B+4C+%2B+C+=+117
Simplify
13C+=+117
Divide both sides by 13
highlight%28C+=+9%29
Now plug 9 into equation 2 for C
Equation 2:B+=+4C
B+=+4%2A%289%29
highlight_green%28B+=+36%29
Now plug 36 into equation 1 for B
Equation 1:A+=+2B
A+=+2%2A%2836%29
highlight%28A+=+72%29