Find the x- and the y-intercept for each of the given equations:
3=4y+x
4y=-x+3
In the first case, if we let x = 0, y turns out to be 3/4. The y-intercept is thus (0, 3/4). If we let y = 0, then x = 3. The x-intercept is (3,0). Plot these two points and draw a line thru them.
In the second case, if let x=0, then y = 3/4. The y-intercept is thus (0, 3/4) (exactly the same as the y-intercept for the previous equation / graph).
Convince yourself that these two equations really contain exactly the same information.
So, if you graph one of them, the 2nd graph will coincide (lie on top of) the 1st.
There are an infinite number of solutions to this system.