Ineed to know the inequality to find the answer to this problem.

To decrease an amount by 16% what single multiplier would you use

Suppose you are choosing a 6-digit personal access code. this code is made up of 4 digits chosen from 1 to 9, followed by 2 letters chosen from a to z. any of these digits or letters can be repeated. find the total number of personal access codes that can be formed. 492,804 341,172 39,917,124 4,435,236

What’s the answer? and how do i solve it ?