-16=6(y-8)-2y

You did not need Wolfram|Alpha Tetration jsut sub your answer in and check it works.

-16=6(y-8)-2y        y=8

RHS=1(8-8)-2*8 = 0-2*8 = -16 = LHS   so it is definitely correct  

Order of operations:

1. Solve the paranthesis

2. Multiply(*) / divide (:)

3. Add (+) / subtract (-)

EITHER:

-16 = 6(y - 8) - 2y                    use the formula a - b = -(b - a) to get rid of minuses:

16 = 6(8 - y) + 2y        

16 = 48 - 6y + 2y = 48 - 4y             Get all numbers over to the right side        

0 = 32 - 4y                                       Move your variable to the left side

4y = 32

y = 8

OR: 

-16 = 6(y - 8) - 2y          Solve the paranthesis:

-16 = 6y - 48 -2y            Combine like terms:

-16 = 4y - 48                   Add 48 to both sides:

32 = 4y 

4y = 32                          Divide both sides by 4:

y = 8

the answer is 

Y  =  -4

I have the Wolfram Alpha page in front of me, and it says that y = 8.