Question

2/3 of the students of the school are girls. if the number of girls is 800. what is the number of student?

Answer 1

x=total number of students
.20x = Number of boys
.80x = Number of girl If 80% are girls, then 20% are boys
.80x=800
x=1000 total students
.20x = .20(1000) = 200 Boys 

Answer 2

Let the number of students be x
Then,Girls=2/3x
According to problem no.of girls is 800
    2/3x=800
  =>2x=800*3
  =>x=800*3/2=1200
therefore no. of students is 1200.