How to generate a linear graph from two (or more) variables?

[#1]

Good Morning to everybody,

I'm a "NEWBIE"  and I've got an issue in generating a linear graph

from two (or more)  variables or from two (or more) values.  I try to Explain with the example below:

I've obtain the first value (45.000.000) and called it variable1

I've obtain the second value (38.000.000) and called it variable2

I'd like to generate a graph like the one showed but

the expression ask me a field from a table that I haven't.

What I have to write in the Expression?

Is there a solution for this kind of issue?

Thanks in advance for any advice.

Macs