Table:
0
A
B
C
D
E
F
1
ship id
name
type
built year
class
flag
2
1
HMS Manxman
Panamax
1/1/1997
KR
Panama
3
2
HMS Gorgon
Panamax
1/1/1998
KR
Panama
4
3
HM Cutter Avenger
Panamax
1/1/1997
KR
Panama
5
4
HM Schooner Hotspur
Panamax
1/1/1998
KR
Panama
6
5
HMS Destiny
Panamax
1/1/1998
KR
Panama
7
6
HMS Trojan
Panamax
1/1/1997
KR
Panama
8
7
HM Sloop Sparrow
Panamax
1/1/1997
KR
Panama
9
8
HMS Phalarope
Panamax
1/1/1997
KR
Panama
10
9
HMS Undine
Panamax
1/1/1998
GL
Malta

Questions and formulas:
Question: how many ships are there?
Formula: SUM(A1)
Formula2: SUM(A2:A10)
Level: easy
Question: Count the number of ships.
Formula: SUM(A1)
Formula2: SUM(A2:A10)
Level: easy
Question: Which flag is most widely used among all ships?
Formula: TAKE(SORT(SUMMARIZE(F1,SUMX(A1)), 2, -1), 1)
Formula2: TAKE(SORT(SUMMARIZE(F2:F10,SUMX(A2:A10)), 2, -1), 1)
Level: hard
Question: Return the flag that is most common among all ships.
Formula: LET(a,HSTACK(F1,A1),b,A1,c,CHOOSECOLS(TAKE(SORT(SUMMARIZE(A1,COUNTX(A1)), 2, -1), 1),1),UNIQUE(FILTER(a,NOT(ISNA(XLOOKUP(b,c,c))))))
Formula2: LET(a,HSTACK(F2:F10,A2:A10),b,A2:A10,c,CHOOSECOLS(TAKE(SORT(SUMMARIZE(A2:A10,COUNTX(A2:A10)), 2, -1), 1),1),UNIQUE(FILTER(a,NOT(ISNA(XLOOKUP(b,c,c))))))
Level: hard
Question: The number of ships.
Formula: SUM(A1)
Formula2: SUM(A2:A10)
Level: easy
Question: How many ships?
Formula: SUM(A1)
Formula2: SUM(A2:A10)
Level: easy
Question: Which flag is most popular among ships?
Formula: TAKE(SORT(SUMMARIZE(F1,SUMX(A1)), 2, -1), 1)
Formula2: TAKE(SORT(SUMMARIZE(F2:F10,SUMX(A2:A10)), 2, -1), 1)
Level: hard
Question: The year when the biggest number of ships were built. 
Formula: TAKE(SORT(SUMMARIZE(D1,SUMX(A1)), 2, -1), 1)
Formula2: TAKE(SORT(SUMMARIZE(D2:D10,SUMX(A2:A10)), 2, -1), 1)
Level: hard
Question: Which flag does most ships have?
Formula: TAKE(SORT(SUMMARIZE(F1,SUMX(A1)), 2, -1), 1)
Formula2: TAKE(SORT(SUMMARIZE(F2:F10,SUMX(A2:A10)), 2, -1), 1)
Level: hard
Question: The year which had most ships built.
Formula: TAKE(SORT(SUMMARIZE(D1,SUMX(A1)), 2, -1), 1)
Formula2: TAKE(SORT(SUMMARIZE(D2:D10,SUMX(A2:A10)), 2, -1), 1)
Level: hard
Question: Total number of ships.
Formula: SUM(A1)
Formula2: SUM(A2:A10)
Level: easy
Question: The number of ships.
Formula: SUM(A1)
Formula2: SUM(A2:A10)
Level: easy