RankX function across multiple Dimension Tables

abhiram342 , refer this

https://www.sqlbi.com/articles/filtering-the-top-3-products-for-each-category-in-power-bi/

For Rank Refer these links
https://radacad.com/how-to-use-rankx-in-dax-part-2-of-3-calculated-measures
https://radacad.com/how-to-use-rankx-in-dax-part-1-of-3-calculated-columns
https://radacad.com/how-to-use-rankx-in-dax-part-3-of-3-the-finale
https://community.powerbi.com/t5/Community-Blog/Dynamic-TopN-made-easy-with-What-If-Parameter/ba-p/367415

abhiram342 - You may find this helpful. 

https://community.powerbi.com/t5/Quick-Measures-Gallery/To-Bleep-with-RANKX/m-p/1042520#M452

Otherwise, Not really enough information to go on, please first check if your issue is a common issue listed here: https://community.powerbi.com/t5/Community-Blog/Before-You-Post-Read-This/ba-p/1116882

Also, please see this post regarding How to Get Your Question Answered Quickly: https://community.powerbi.com/t5/Community-Blog/How-to-Get-Your-Question-Answered-Quickly/ba-p/38490

The most important parts are:
1. Sample data as text, use the table tool in the editing bar
2. Expected output from sample data
3. Explanation in words of how to get from 1. to 2.

Hi abhiram342 ,

You can use this measure

Top 3 = 
SWITCH(
    TRUE(),
    ISINSCOPE(Customer[Name]), RANKX(ALL('Customer'[Name]),[Total Sales]),
    ISINSCOPE('Item'[Brand]), RANKX(ALL('Item'[Brand]), [Total Sales])
)

Create a Visual Filter where Top3 is less than 3.

Regards,
Harsh Nathani
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// Create a measure that for each
// customer will tell you if
// they are in the top 3 cust for
// a product or not. Then use the measure
// as a filter for a table visual that will
// show you the existing combinations
// of Product and Customer and will display
// the [Total Sales] measure. Filter the
// visual by [Filtering Measure] = 1.

[Filtering Measure] =
var __oneProductAndCustomerVisible =
    HASONEVALUE( Customer[CustID] )
    && HASONEVALUE( Product[ProdID] )
var __result =
    if(
        __oneProductAndCustomerVisible,
        var __top3Customers =
            CALCULATE(
                // Bear in mind that if there
                // are ties with respect to
                // [Total Sales], all the qualified
                // customers will be returned, so
                // there might be more than 3.
                topn(3,
                    VALUES( Customer[CustId] ),
                    [Total Sales],
                    DESC
                ),
                ALL( Customer )
            )
        var __currentCustInTop3 =
            VALUES( Customer[CustID] )
            in __top3Customers
        return
            1 * __currentCustInTop3
    )
return
    __result