Can you explain what you are trying to solve for here? This is a linear equation. If you graph it you will see that it produces a line on the graph. Here is the graph:
Any point alone the line provides a possible solution to the problem.
you can also write this in slope-intercept form by solving for y
subtract x from both sides to get
y=-x+4
This shows that the slope is -1 and the y intercept is 4
y=mx+b
m=slope, in this case the x has just the - in front of it which is the same as -1
b=y-intercept. This is +4
Hopefully that helps.