How to count rows of column after a filter expressions (not using calculate)

[ARK8]

Table Customer 

Customer Key	Customer Type
1	L
2	S
3	L
4	S

Sales Table 

Sale Qty	Sale price	Customer ID
50	2	1
20	5	2
10	10	3
100	30	4
200	8	3

I am trying to count distinct customers for a particular type  who made sale using Filters (strictly not by calculate) 
 So far I came up with this : 

    FILTER ( Sales,

                  Related(Customer[CustomerType] = "L"

               )

 not sure who do I go from here.

[tamerj1 · Accepted solution]

Hi @ARK8 

Please try

Count =
COUNTROWS (
SUMMARIZE (
FILTER ( Sales, RELATED ( Customer[CustomerType] ) = "L" ),
Customer[Customer Key]
)
)