How many flights of Alaska Airlines were delayed on 2018/8/2?
Alaska Airlines refers to Description = 'Alaska Airlines Inc.: AS'; delayed refers to DEP_DELAY > 0; on 2018/8/2 refers to FL_DATE = '2018/8/2';
SELECT COUNT(*) FROM Airlines AS T1 INNER JOIN `Air Carriers` AS T2 ON T1.OP_CARRIER_AIRLINE_ID = T2.Code WHERE T1.FL_DATE = '2018/8/2' AND T2.Description = 'Alaska Airlines Inc.: AS' AND T1.DEP_DELAY > 0