If the difference of a number and four is doubled the result is 1/4 less than the number. find the number

The formula is  (2)(n-4) = n-1/4

Mult both sides by 4: 

                         8n - 32 = 4n -1, or 4n = 31, or n=31/4.

If this is not what you expected, please ensure that you have copied down the original problem correctly.  What do you mean by "1/4 less?"

Let's try    (2)(n-4) = 1n-(1/4)n = (3/4)n.  Then,

2n-8 = (3/4)n, or (5/4)n = 8.  Mult. both sides by (4/5), we get:

n = (5/4)(8) = 10.  Is that what you were hoping for?

How many groups are there?