Respuesta :

cdw2014
You have the equations set up correctly. I will use r and b as the variables to make it easier to follow.

12r + 8b = 70
20r + 12b = 110

First let's solve one of the equations for one of the variables.

12r = 70 - 8b

[tex]r = \frac{70-8b}{12} [/tex]

Now plug that in for r in the second equation.

[tex]20( \frac{70-8b}{12})+12b = 110 [/tex]

Simplify

[tex]20(70-8b)+144b=1320[/tex]

[tex]1400-160b+144b=1320[/tex]

[tex]-16b = -80[/tex]

b = 5 grams

Now plug 5 in for b in one of the original equations to find r.

12r + 8(5) = 70

12r  = 30

r = 2.5 grams

So the red marbles weigh 2.5 grams, and the blue marbles weigh 5 grams.

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