This is an EITHER/OR group problem.
Every employee is EITHER a man OR a woman.
Every employee is EITHER married OR single.
For an EITHER/OR group problem, we can use a GROUP GRID (also known as a double-matrix) to organize the data.
Since the total number of workers = 50, we get the following grid:

In the grid above, the entries in any given row or column must add up to the TOTAL of that row or column:
In the top row, married women + married men = total married.
In the middle column, married women + single women = total women.
Question stem, rephrased:
What is the difference between the number of married men and the number of single women?
Statement 1:

No information about the number of married men.
INSUFFICIENT.
Statement 2:

No information about the number of married men or the number of single women.
INSUFFICIENT.
Statements combined:

Thus, single women - married men = 15-10 = 5.
SUFFICIENT.
The correct answer is
C.
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