Question

There are 27 pupils. There are twice as many boys than girls. how many boys and girls are there

Answer 1

No. of boys=2x
no.of girls=x
total no. of pupils=2x+x
27=3x
27/3=x
x=no.of girls=9
no.of boys =2x=2*9=18

Answer 2

Let x  =  the numbers of girls
thus
the numbers of boys  = 2x 
x + 2x = 27
3x = 27
x = 9
2x = 2 . 9 =18
girls  =  9  &  boys  = 18