Question 198240
sol;
let the total numbe of students in a  class be 100
60%of the class=60/100*100=60
boys in the class=60
total students in the class=100
girls in the class=100-60=40
later 6 girls are move away
now toal number of students=100-6=94
and againg 6 girls are replace by 6 boys 
now total number of students in the class=94+6=100
now 75% of the class=75/100*100=75
now number of boys in a class =75 
number of girls in the class=100-75=25