Table:
0
A
B
C
D
E
1
customer id
payment method
customer name
date became customer
other customer details
2
1
Cash
Dr. Julia Wuckert MD
3/1/2018 23:20
3
2
Cheque
Tillman Ernser
2/28/2018 11:37
4
3
Credit Card
Rodrick Heaney
3/9/2018 17:41
5
4
Credit Card
Prof. Alexzander Hamill
2/24/2018 0:20
VIP
6
5
Cheque
Prof. Reyes Berge II
3/7/2018 18:05
7
6
Cash
Maudie Kertzmann
2/26/2018 11:57
8
7
Credit Card
Mozell Morissette
2/25/2018 13:15
VIP
9
8
Credit Card
Eunice Morar
3/21/2018 1:01
10
9
Cheque
Devin Mills
3/5/2018 16:52
11
10
Cash
Kitty Padberg III
3/22/2018 18:09
12
11
Cheque
Salvatore Tillman
3/4/2018 0:17
13
12
Cheque
Clifford Pagac
2/24/2018 10:24
14
13
Credit Card
Miss Aliyah Witting
3/5/2018 7:19
15
14
Cheque
Alexane Kilback
3/8/2018 1:17
16
15
Cash
Prof. Ibrahim Bashirian
3/15/2018 2:54

Questions and formulas:
Question: Names of customers who pay in cash
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,B1="cash"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E16,B2:B16="cash"),3))
Level: medium
Question: the ids and names of customers who pay in cash
Formula: LET(query1,FILTER(A1:E1,B1="cash"),UNIQUE(CHOOSECOLS(query1,1,3)))
Formula2: LET(query1,FILTER(A2:E16,B2:B16="cash"),UNIQUE(CHOOSECOLS(query1,1,3)))
Level: hard
Question: most common payment method 
Formula: TAKE(SORT(SUMMARIZE(B1,COUNTX(B1)), 2, -1), 1)
Formula2: TAKE(SORT(SUMMARIZE(B2:B16,COUNTX(B2:B16)), 2, -1), 1)
Level: hard
Question: What are the payment methods?
Formula: UNIQUE(B1)
Formula2: UNIQUE(B2:B16)
Level: easy
Question: What are payment methods and ids of customers?
Formula: UNIQUE(HSTACK(B1,A1))
Formula2: UNIQUE(HSTACK(B2:B16,A2:A16))
Level: easy
Question: What are names and ids of customers?
Formula: UNIQUE(HSTACK(C1,A1))
Formula2: UNIQUE(HSTACK(C2:C16,A2:A16))
Level: easy
Question: all customers' names and ids 
Formula: UNIQUE(HSTACK(C1,A1))
Formula2: UNIQUE(HSTACK(C2:C16,A2:A16))
Level: easy
Question: Names of customers don't pay in cash?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,B1<>"cash"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E16,B2:B16<>"cash"),3))
Level: medium
Question: Who doesn't pay in cash?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,B1<>"cash"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E16,B2:B16<>"cash"),3))
Level: medium
Question: the name and id of customer
Formula: UNIQUE(HSTACK(C1,A1))
Formula2: UNIQUE(HSTACK(C2:C16,A2:A16))
Level: easy
Question: the name of customer who pays in cash
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,B1="cash"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E16,B2:B16="cash"),3))
Level: medium
Question: the payment method used by most customers.
Formula: TAKE(SORT(SUMMARIZE(B1,SUMX(A1)), 2, -1), 1)
Formula2: TAKE(SORT(SUMMARIZE(B2:B16,SUMX(A2:A16)), 2, -1), 1)
Level: hard
Question: Any payment methods?
Formula: UNIQUE(B1)
Formula2: UNIQUE(B2:B16)
Level: easy
Question: the name of customer who doesn't pay in cash
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,B1<>"cash"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E16,B2:B16<>"cash"),3))
Level: medium