Working together, Alex and Millie can file all the papers in the file cabinets in 4 hours. It would have taken Alex 6 hours to do the job alone. What is the missing value in the table that represents the part of the papers that Alex would file if Alex and Millie worked together?

You can use this formula:

T = AM/A+M, where

T - total number of hours of Alex and Millie's work

A - Alex's time

M - Millie's time

It will now be:

4 = 6M / 6+M

6+M (4) = 6M (6+M) / 6+M

24 + 4M = 6M (1)

24 + 4M = 6M

24 = 6M - 4M

24 = 2M

To get Millie's time, divide 2M and 24 into 2 (2M/2 = 24/2).

Millie's time = 12 hours