How To Calculate Total Matrix Using Average

Hi pisca 
You may try

Total Weight =
SUMX (
    SUMMARIZE ( 'Table', 'Table'[product_name], 'Table'[invoice-number] ),
    [Quantity (Pack)] * [Weigh (kg)]
)

So, I create a measure quantity like this

quantity = 
    SUMX(
        SUMMARIZE(
            'table',
            'table'[product_name],
            'table'[inv_number]
        ),
        CALCULATE(
            AVERAGE(
                'table'[quantity]
            )
        )
    )

and then, I made one more measure weight like this

weight = 
    SUMX(
        SUMMARIZE(
            'table',
            'table'[product_name],
            'table'[inv_number]
        ),
        CALCULATE(
            AVERAGE(
                'table'[product_weight]
            )
        )
    )

 last, I made one more measure total weight like this

totalweight = 
SUMX(
     SUMMARIZE(
               'table',
               'table'[product_name],
               'table'[inv_number]
     ),
     [quantity] * [weight]
)

the results were as I expected.

Thanks tamerj1