DAX , Filter using values from table column

Hi,

I have posted, almost the same question on Mr Excel ;
https://www.mrexcel.com/board/thread...table.1252088/

I would like to filter a table down twice and see the "Item" values that are in both, in power query which I have attacched;

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But I have been trying to do this in DAX but have two problems,
I can get what I want by filtering and then taking the values and hardcoding them in so A, B and C values returned in 'atable' ;

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But what I am trying for is someting along the lines of ;

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I think that SUMMARIZE( btable,[Item] ) would give same as { "D","C"}
I have go a result using Filter and Or ||


I have attached my starting point, what I've done so far has been in studio rather than on file .


Richard