So I am trying to change my money variable but every time I try to change it, I try to subtract from it using:

change [ v] by (-100000)

But every time it comes up as: “NaN”

You should decrease the value.

• change [ v] by (-1)

NaN is an abbreviation for “not a number”. If your variable had the value “hello” and you try to subtract a number from it, you'll get NaN.
Make sure the variable starts out with a number, and you should be able to subtract from it and get another number:

when green flag clicked
set [Money v] to [100]

That still gives me the NaN when I define what the variable is.

Share the project please.

EDIT: I see you've made another topic about this, and your problem was already answered there:
https://scratch.mit.edu/discuss/post/3220972/




I'm going to hazard a guess that perhaps you included the currency symbol when you set the variable's value?

So maybe you've got something like "set var to [$100]“ in your project…?

If so, that means the variable does not really have a numerical value (it's a ‘string’ of characters rather than a number), and that means you cannot do arithmetic on it.

A variable must have a numerical value if you want to use ”change var by …" on it, so it cannot contain other characters such as the $ symbol, etc.