Question

the number of boys and girls in a class are in the ratio 75 the number of boys is 8 more than the number of girls what is the total class strength

Answer 1

Let
Boys = b
Girls = g 


The number of boys and girls in a class are in the ratio 7:5
b:g=7:5
b/g=7/5
b5=g7
b5/5=g7/5
b=g7/5...............(1) 
the number of boys is 8 more than the number of girls

b=g+8.............(2)
Put the value of b from (1) to (2)
g7/5=g+8
5*(g7/5)=5*(g+8)
g7=5g+40
g7-g5=40
2g=40
2g/2=40/2
g=20
Put the value of g in (2)
b=20+8
b=28 
Boys are 28 and Girls are 20

Answer 2

girls= 5x
boys= 7x
7x-5x= 8
2x= 8
x= 8/2=4
boys = 7x= 7*4= 28
girls = 5x = 5*4 = 20
total= 28+20= 48