Question 6561
let the number of boys be x1.number of girls be x2.

x1+x2 = x

Given that x1/x2 = 2/3

====> 3x1-2x2=0 ----->equation (1)

after adding 

x1+2/x2+7 = 3/5

====> 5x1-3x2=11 ----->equation (2)

sloving 1 and 2 ,

we get x1,x2 as 22,33 respectivly.

So the total is 55 students.