Separate positive & negative numbers from on cell

If you want then you can get directly answer which is 20 in the given case. You need to just remove first quotation which you added.

Regards,
Suhas

That still leaves the separating positive and negative numbers results.

I think you need to look at why the data is in this format in the first place.
You may be able to solve this a lot easier if you're able to change the data before it gets to this stage.