soleve this equation by graph
[y=x+1 ] [y=-x+3]
Graph both equations on the same axes.
If the two lines intersect, that tells you the two equations, for that value of x, return the same y. x is your solution to the two equations.
If the lines are parallel, That means one line is actually the other line shifted up or down. There's no x that gives the same y in both equations at the same time. So, there's no solution for that set of equations.