The width of a rectangular painting is 5 inches shorter than it's width. my question is, if i where to make a table, what would be the width, length, and area?

I'm guessing you meant the length is 5 in. shorter than the width.

I'll use L, W, and A to represent length, width, and area, respectively.

We know the area of a table, which is a rectangle, is given by A = L * W.
We also know that L = W - 5.
And then W = W, pretty much.

So, given any width W, we can find L and A.

Width is W
Length is L = W - 5
Area is A = L * W, but let's replace L with (W - 5).
A = (W - 5) * W
A = W^2 - 5W