can anyone help to understand chargeable gain I am really struggling with this

Sale proceeds £12,000
Less cost (w1) £6000
Chargeable Gain £6000

(W1)
MV of the whole asset at the time of sale is 12000+40000 = 52000
So the asset with the MV of 52000 has an original cost of £26000
Cost apportioned to the part of the asset that has been sold: 12,000*26000/52000 = 6000

Hello Annie, the question you have (i.e. on Peter) is a parts disposal. Therefore, the cost of the part disposed is expressed as Cost * A/A+B where A = value of part disposed, B = market value of remaining asset.
Thus, you would proceed with the chargeable gains pro-forma same way, see below

Disposal Proceeds 12,000
Less Incidental Cost (500)
Net Proceeds: 11,500
Less Allowable Cost (6,000)
26,000 * 12,000/(12,000+40,000)
Chargeable Gains 5,500

Don’t forget, the incidental cost incurred relates to the parts disposal and is brought into the gains computation as a deduction from your disposal proceeds.

On how to approach a chargeable gains question, from my understanding on the open tuition videos, the main problem is knowing what allowable cost to associate with the disposal i.e. the other elements e.g. disposal proceeds etc are given in the question. To know what cost you need to know what asset is being disposed i.e. is it exempt, is a chattel, is it a non-chattel wasting asset, is it shares/securities, is it a part disposal etc..once you figure that out, apply the rules. Always also know that any incidental cost always relate to that disposal at hand, always bring it in.

I have captured my understanding thus far, also go thru the open tuition lectures, they are amazing.