Ok! This is an activity. Heres what you do.

Write SLEEP NIGHT on a piece of paper
The label them from 0 9

You will have something like this.

S L E E P N I G H T
0 1 2 3 4 5 6 7 8 9

Select 3 different numbers ie; 587

Work backwards from 587 and you get 785
Then the difference between 587 and 785 should be = (A)
Work backwards again with (A) and you should have (B)
Add up (A and B) = C
Multiply (C) by 40 and you should have (D)

Substitute all the numbers (D) with the alphabet (From sleep Night) and you will have the answer
Have fun with this activity