Homework Help: Math

Posted by Me on Friday, April 9, 2010 at 3:15pm.

Help pls! I just need to set the equations only, I can do the rest. The qu. Is:
The sum of three numbers is 15. The sum of the first, the second, and twice the third is 20. The sum of the first, twice the second, and three times the third is 27.
This is what I did:
1st # = x
2nd # = y
3rs # = z
so
x+y+z=15
x+y+2z=20
x+2y+3z=27
then solved by elimination of z, and finally got (16,10,-1)
where is my mistake?
Where is my mistake?

Math - Damon, Friday, April 9, 2010 at 3:26pm
2x+2y+2z = 30
x + y+2z = 20
---------------
x + y = 10

3x+3y+3z = 45
x +2y+3z = 27
-----------------
2x + y = 18

gives
2x+2y = 20
2x +y = 18
-----------
y = 2 (not 10)

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