Answer:
11
subtract 3
Step-by-step explanation:
The numbers are getting lower in value as you go,
So that means it is a subtracting sequence,
Take the first two numbers and subtract them,
23 - 20 = 3
So now subtract 3 from the others and see if it works,
20 - 3 = 17
17 - 3 = 14
14 - 3 = 11
11 is the missing number
Yep, it works,
Hence the sequence is to subtract three.
