Question

How can I add these two equations in order to solve for y?
y=(1/2x)-1
y=((-2)x)+4

Answer 1

Multiply each side of the first equation by 4.
The add the equations together. The x terms will subtract out.

Answer 2

how are these exactly ?

1
y = ---x - 1
2
(-2)x
y= -----
4

in this way is right ?

Answer 3

4 y = (2 x) - 4
y = -2x + 4

y = 0
x = 2