Table:
0
A
B
C
1
registration id
date test taken
test result
2
12
3/25/2018 3:27
Fail
3
10
3/25/2018 21:50
Pass
4
7
3/21/2018 0:32
Pass
5
7
3/25/2018 0:44
Pass
6
4
3/25/2018 15:06
Pass
7
16
3/25/2018 12:00
Fail
8
16
3/25/2018 21:22
Fail
9
19
3/24/2018 13:22
Pass
10
19
3/25/2018 16:59
Fail
11
4
3/25/2018 21:41
Fail
12
9
3/19/2018 2:04
Pass
13
5
3/22/2018 17:07
Fail
14
17
3/23/2018 23:47
Pass
15
2
3/22/2018 13:10
Fail
16
2
3/19/2018 14:48
Pass

Questions and formulas:
Question: Find the dates of the tests taken with result "Pass".
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:C1,C1="pass"),2))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:C16,C2:C16="pass"),2))
Level: medium
Question: How many tests have result "Fail"?
Formula: ROWS(FILTER(A1:C1, C1="fail"))
Formula2: ROWS(FILTER(A2:C16, C2:C16="fail"))
Level: easy
Question: Count the number of tests with "Fail" result.
Formula: ROWS(FILTER(A1:C1, C1="fail"))
Formula2: ROWS(FILTER(A2:C16, C2:C16="fail"))
Level: easy
Question: Date when the test was both taken and passed.
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:C1,C1="pass"),2))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:C16,C2:C16="pass"),2))
Level: medium
Question: How many tests were failed? 
Formula: ROWS(FILTER(A1:C1, C1="fail"))
Formula2: ROWS(FILTER(A2:C16, C2:C16="fail"))
Level: easy
Question: How many test results were fails?
Formula: ROWS(FILTER(A1:C1, C1="fail"))
Formula2: ROWS(FILTER(A2:C16, C2:C16="fail"))
Level: easy
Question: the taking date of the passed test 
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:C1,C1="pass"),2))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:C16,C2:C16="pass"),2))
Level: medium
Question: The number of fail tests.
Formula: ROWS(FILTER(A1:C1, C1="fail"))
Formula2: ROWS(FILTER(A2:C16, C2:C16="fail"))
Level: easy
Question: How many tests are failed?
Formula: ROWS(FILTER(A1:C1, C1="fail"))
Formula2: ROWS(FILTER(A2:C16, C2:C16="fail"))
Level: easy