A simple ratio can give you the numbers you need. M:F ratio is given at 10:15. So then, 10/15 = 50/f. Solve to get f=75. So, if there are 50 male employees, there must be 75 female employees.
50 males divided by 50+75 (total employees) gives 50/125, or 0.4. Converting to a percentage, 40% of the employees are male.