Two models of cellular telephones, red and blue, are stored in boxes. One box weighs twelve pounds and contains four of the red models and one blue model. Another box weighs eight pounds and contains one blue model and two red models. How much does each model weigh?

First, make a equation in which r = red and b=blue.

So, since in the first box it has 4 red models and one blue model equaling 12,

the first equation looks like 4r+b=12.

The second equation looks like 2r+b=8.

What you would do is try and first solve for r by getting rid of b.

Since both equation has a positive b, you would make one equation have a negative b by multiplying the whole equation by - 1.

-1 * (2r+b=8) = - 2r-b=-8

Add.

4r+b=12

+ (-2r-b=-8)

2r=4

r=2

Then, you plug in 2 for the r for any of the original equations.

4 (2) + b=12

8+b=12

b=4

or

2 (2) + b=8

4+b=8

b=4

So, the red models weigh 2 pounds while the blue models weigh 4.