**Edit:** Let me put it to you this way:

You have some known weights which you measure with your scale to produce inaccurate weights. These values are all known, so you can consider each weight and measurement as the coordinates of a point on a curve: the

-coordinate being the actual weight, and the

-coordinate being the measured weight. You have done this, and you have a line (or something that resembles a line reasonably closely). This means that you can find the slope of the line, and its

-intercept, and using these you can represent the line as an equation that relates

to

.

Thus, the solution to your problem comes down to this: if you have an object of

*known* weight, you are able to simply locate the point on the line with that

-coordinate, and the

-coordinate will be the measured weight (which would be the reading you would get off of your scale). But your problem is the reverse: you have a

*measured* weight, and you wish to find the actual weight. Thus you find the point on the line with the particular

-coordinate, and the

-coordinate of that point will be the actual weight.

So how do you put this into a convenient formula where you can just "plug in" the measured value? Simple: as I said, you already know the measured value in terms of the actual value (

), so you just solve for the actual value in terms of the measured value

. So if your scale gives a measurement of

, the actual weight would be

. Does that make sense?