If 15 is 25% of a value, what is that value?

In the given question it is already given that 15 is the 25% of a certain unknown number. Using these information’s the unknown number can be found easily.
Let us assume the unknown value to be = x
Then we can write the equation as
25x/100 = 15
25x = 15 * 100
25x = 1500
x = 1500/25
  = 60
So the unknown number is 60. Hope this is what you were looking for and the procedure of doing the problem is clear enough.

Ibelieve the answer would be 7, 13, 23