--76
WITH TWICE(ID) AS (SELECT  p1.ID_psg
FROM Pass_in_trip p1 JOIN Pass_in_trip p2
ON p1.ID_psg=p2.ID_psg and p1.place = p2.place and (p1.trip_no!=p2.trip_no OR( p1.trip_no=p2.trip_no AND p1.date<>p2.date)
))

SELECT name , s
FROM ( SELECT distinct ID_psg, sum(
     CASE
     WHEN DATEDIFF(mi,time_out,time_in)>=0
     THEN (DATEDIFF(mi,time_out,time_in))
     ELSE (DATEDIFF(mi,time_out,time_in)+1440)
     END ) s
       FROM Pass_in_trip p  JOIN Trip t  ON   t.trip_no=p.trip_no
       WHERE ID_psg NOT IN (SELECT distinct ID FROM TWICE)
       GROUP BY ID_psg) tmp
JOIN Passenger pa ON pa.ID_psg=tmp.ID_psg

--78
SELECT name, REPLACE(CONVERT(CHAR(12), DATEADD(m, DATEDIFF(m,0,date),0), 102),'.','-') f,
             REPLACE(CONVERT(CHAR(12), DATEADD(s,-1,DATEADD(m, DATEDIFF(m,0,date)+1,0)), 102),'.','-') l
FROM Battles

--80
SELECT DISTINCT maker
FROM product
WHERE maker NOT IN (  SELECT maker
     	              FROM product
    	              WHERE type='PC' AND model NOT IN (SELECT model FROM PC))

--84
SELECT name,sum(f) f,sum(s) s, sum(th) th
FROM
(SELECT  ID_comp,
CASE WHEN DATEDIFF(dd,'20030401',date)>=0 and DATEDIFF(dd,date,'20030411')>0
     THEN COUNT(ID_psg)
     ELSE 0
END f,
CASE WHEN DATEDIFF(dd,'20030411',date)>=0 and DATEDIFF(dd,date,'20030421')>0
     THEN COUNT(ID_psg)
     ELSE 0
END s,
CASE WHEN DATEDIFF(dd,'20030421',date)>=0 and DATEDIFF(dd,'20030430',date)<=0
     THEN COUNT(ID_psg)
     ELSE 0
END th
FROM Trip t JOIN Pass_in_trip p ON p.trip_no=t.trip_no and CONVERT(char(6), P.date, 112) = '200304'
GROUP BY ID_comp,date) t JOIN Company c ON c.ID_comp=t.ID_comp
GROUP BY name