Kelly is making a chart to show her parents that the number of minutes she spoke on her cell phone decreased over the last 5 months. which set shows her cell phone minutes decreasing?
a.
{756.58, 1259, 2009.03, 2920, 3452.63}
b.
{3452.63, 2920, 2009.03, 1259, 756.58}
c.
{756.58, 3452.63, 2920, 2009.03, 1259}
d.
{1259, 2009.03, 2920, 3452.63, 756.58}

(-4, -3)

Step-by-step explanation:

Using elimination by addition and subtraction works best here.

Suppose we decide to eliminate x temporarily.  To do this, we multipy the first row by 4, obtaining

-12x + 28y = -72

  4x  - 4y   =   8

Next, multiply the second row by 3, obtaining the "equivalent system"

-12x + 28y = -72

  12x - 12y   =  24

Combining these equations, column by column, we get:

16y = -48.  So y = -3.

Now let's find x.  Substitute -3 for y in the second equation:

4x - 4(-3) = 8, or

4x + 12    = 8, or

4x            = 8 - 12  = -4.  This tells us that x = -4.

The solution is thus (-4, -3).