An example:

You can use more than one "work" column to get to the result.

. Known   Work    Work    Result
---------------------------------
|  16   |  48   |  24   |  12   |
|--------------------------------
|  28   |  84   |  42   |   X   |
---------------------------------

First row logic:

(((16 * 3) / 2) / 2) = 12 (there are other solutions other than * 3 / 2 / 2)
((48 / 2) / 2) = 12
24 / 2 = 12


Use same logic on second row:

(((28 * 3) / 2) / 2 = X
((84 / 2) / 2) = X
42 / 2 = X
21 = X


The one I can't solve without fractions or decimals.

This is how the table looks (could be more than one "work" column though).

. Known   Work    Result
-------------------------
|  50   |       |  18   |
|------------------------
|  60   |       |   X   |
-------------------------