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math_dude16 · Mar 13, 2009, 08:37 AM

Could someone please help me! This problem with elimination not SUBSITUTION:

Nn+ Nd= 50
5Nn+10Nd= 450

galactus · Mar 13, 2009, 01:16 PM

N is a constant and n and d are the variables.

$Nn+Nd=50$
$5Nn+10Nd=450$

Multiply the top equation by -5. See why? We have to find a number that eliminates a variable. In this case, -5+5=0. So, we have:

$-5Nn-5Nd=-250$
$5Nn+10Nd=450$

Add them:

$5Nd=250$

$d=\frac{50}{N}$

Now, you find n.

asastring · Mar 13, 2009, 06:57 PM

5Nd = 200
d=40/N