Week over week measure

JC2022 
Aplogies again for the late response.
I hope the following fulfils your requirement.

DaysOpen = 
VAR MinDate =
    MIN ( 'dim_date'[Date] )
VAR MaxDate =
    MAX ( 'dim_date'[Date] )
RETURN
    AVERAGEX (
        CALCULATETABLE ( 
            VALUES ( CurrentRow_tasks[taskKey] ),
            CurrentRow_tasks[taskCreatedDateDK] <= MaxDate,
            OR (
                CurrentRow_tasks[BusinessClosingDateDK] > MinDate,
                ISBLANK ( CurrentRow_tasks[BusinessClosingDateDK] )
            ),
            REMOVEFILTERS ( 'dim_date' )
        ),
        CALCULATE (
            VAR CreatedDate =
                MAX ( CurrentRow_tasks[taskCreatedDateDK] )
            VAR ClosedDate =
                COALESCE ( MAX ( CurrentRow_tasks[BusinessClosingDateDK] ), MaxDate )
            RETURN
                DATEDIFF ( CreatedDate, MIN ( ClosedDate, MaxDate ), DAY ),
            CurrentRow_tasks[taskCreatedDateDK] <= MaxDate,
            OR (
                CurrentRow_tasks[BusinessClosingDateDK] > MinDate,
                ISBLANK ( CurrentRow_tasks[BusinessClosingDateDK] )
            ),
            REMOVEFILTERS ( 'dim_date' )
        )
    )