Question 54434
I'm assuming this is supposed to be solved without using matrices, if not, feel free to e-mail me and ill type up a new solution:

To solve by substitution, we need to isolate one variable and then plug the value of that variable into the second  equation:
8x - 4y =16 
y=2x-4
This is saying that x and y are the same numbers for both equations so we can plug the value of y (given in equation 2) into equation 1
8x -4(2x-4) =16
Multiply the coefficient of y through the brackets to get:
8x -8x +16 =16  so basically 16=16

This system is dependant, x could be either 0 or (1/2y+2)