Hello!
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Looking at the graph, we can see that both of the lines intersect at a single point.
Looking at the intersection point, we get an x value of x = 3.
*This can also be proven algebraically by setting the two equations equal to each other:
x + 3 = 4x - 6
3 = 3x - 6
9 = 3x
9/3 = 3x/3
x = 3