The difference of a number and 5 is at most 20 x -5> 20 x -5 greater = 20 right

Answer 1

x - 5 ≤ 20

"at most" means it can't go over 20, so it has to be less than.

Your expression said > 20

Furthermore, by saying the difference between a number and 5, you don't say which way we are subtracting.
e.g. if I say what is the difference between 2 and 10 you would probably say 8, without really caring that 10-2 = 8 but 2 - 10 = -8

so the correct answer would be

|x - 5| ≤ 20