Question 309698
number of ways of arrangement the 3 letters (Gui) = 3! = 3 * 2 * 1 = 6
number of ways of arrangement the 4 numbers (1947) = 4! = 4 * 3 * 2 * 1 = 24


if the arrangement started by the letters than followed by the numbers, then number of ways of arrangement 7-character screen name is:
6 * 24 = 144 ways