This is the system of two equations in two unknowns x and y:



Start writing the first equation down,

-2x - 2y = 16

except when you come to "y", don't write "y"; instead write what
"y" equals from the second equation, putting it in parentheses, 
which is "(-)".  So you write this:

-2x - 2(-8) = 16

Now we replace 2(-8) by the number (-16)

-2x - (-16) = 16

Now we use the definition of subtraction which
tells us that subtracting a negative number isd
adding the opposite positive number: 

Next we add -16 to both sides:

-2x + 16 = 16
    - 16  -16
-------------
-2x      = 0

Now we want to have just x on the left,
so we divide both sides by the coefficient
of x, which is -2



Then we cancel the -2's on the left 



which leaves



and do the division of 0 by -2 on the right, getting 0



So 0 is the solution for x.

The solution for the system of equations is (x,y) = (0,-8)

Edwin