Answer:
The given equation which is in two variable is
⇒2 x + y =9
As we know that to get a unique solution you need two intersecting lines.
But here only one line is given.
On a single line there lie infinite number of points.
So, for different values of x we get different values of y or different values of y we get different values of x.
So , we can write the above equation as
either ⇒y=9-2 x Or x=9-2 y
I have drawn graph for you.
Thus , there are infinite number of solution of this equation. Like (0,9),(1,7),(2,5),(-2,13),(-1,11),(-3,15)......