Can I claim my ex wife who lives with me but hasn’t worked and how much would it help.

[MinhT]

As you are no longer married, you can claim her as a dependent if she passes all the following tests:

1. The person can't be your qualifying child or the qualifying child of any other taxpayer. 
2. The person must live with you all year as a member of your household (and your relationship must not violate local laws). 
3. The person's gross income for the year must be less than $4,050. 
4. You must provide more than half of the person's total support for the year.
5. The person is a U.S. citizen, U.S. resident alien, U.S. national.
6. The person is not a married person who files a joint return unless that joint return is filed only to claim a refund of withheld income tax or estimated tax paid.

Claiming her as a dependent gives you an exemption of $4,050. How much that would save you in tax depends on your tax bracket.