Oracle 18c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE table_name ( date_value, added_weekdays ) AS
SELECT DATE '2021-07-07', 10 FROM DUAL UNION ALL
SELECT DATE '2021-07-07', 11 FROM DUAL UNION ALL
SELECT DATE '2021-07-07', 12 FROM DUAL UNION ALL
SELECT DATE '2021-07-07', 13 FROM DUAL UNION ALL
SELECT DATE '2021-07-10',  0 FROM DUAL UNION ALL
SELECT DATE '2021-07-10',  1 FROM DUAL;
6 rows affected

ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD (DY)';
SELECT date_value,
       added_weekdays,
       weekday_date_value
       + MOD(added_weekdays, 5)        -- Number of days of part week
       + FLOOR(added_weekdays / 5) * 7 -- Number of full weeks
       + CASE TRUNC( weekday_date_value + MOD(added_weekdays, 5) )
              - TRUNC( weekday_date_value + MOD(added_weekdays, 5), 'IW' )
         WHEN 5 THEN 2
         WHEN 6 THEN 1
         ELSE 0 END                    -- Shift value if it falls on a weekend.
         AS final_value
FROM   (
  SELECT t.*,
         date_value
         + CASE TRUNC(date_value) - TRUNC(date_value, 'IW')
           WHEN 5 THEN 2
           WHEN 6 THEN 1
           ELSE 0 END AS weekday_date_value -- Shift the start date if it is on
                                            -- a weekend. 
  FROM   table_name t
)


DATE_VALUE
ADDED_WEEKDAYS
FINAL_VALUE


2021-07-07 (WED)
10
2021-07-21 (WED)

2021-07-07 (WED)
11
2021-07-22 (THU)

2021-07-07 (WED)
12
2021-07-23 (FRI)

2021-07-07 (WED)
13
2021-07-26 (MON)

2021-07-10 (SAT)
0
2021-07-12 (MON)

2021-07-10 (SAT)
1
2021-07-13 (TUE)

DATE_VALUE	ADDED_WEEKDAYS	FINAL_VALUE
2021-07-07 (WED)	10	2021-07-21 (WED)
2021-07-07 (WED)	11	2021-07-22 (THU)
2021-07-07 (WED)	12	2021-07-23 (FRI)
2021-07-07 (WED)	13	2021-07-26 (MON)
2021-07-10 (SAT)	0	2021-07-12 (MON)
2021-07-10 (SAT)	1	2021-07-13 (TUE)