Suppose a certain religious university has a ratio of approximately 90 males to 125 females enrolled as a students. if he current enrollment at the university is 15000 and every male on campus asks a female student to a dance, how many women will be without dates to the dance?

How many males and how many females would there be if the total enrollment is 15000?

Ratio is 

  90 males      15000 - x
  =
   125 fem              x

Then 90x = 1875000 - 125x, or 215x = 1875000

                                                      x = approx 8720 females
                       and 15000-8720, or 6279 males

If every male finds a dance partner, that would leave (8720-6279) females, or 2440, without dance partners.  ;(

Check:  is the male:female ratio near 90:125?

Is 6279:8720 approx equal to 90:125?

Yes.  0.72 (approx) = 0.72 (approx).