Answer:
27
Step-by-step explanation:
Given that the total number of people protesting is 81. These people are either male - Student or non student or Females (student or non students)
Given that there are 36 males then number of females
= 81 - 36
= 45
If there are 18 females non students then the number of females protesting that are students
= 45 - 18
= 27