MATHS``

Let x be the number of girls in F.1A
then, (1+1/3)x = 4x/3 is the number of boys in F.1A

x + 4x/3 = 42 (Total number of students in F.1A)
7x/3 = 42
x/3 = 6
x = 18

So, there are 18 girls in F.1A.
Also, there are:
4(18/3)
= 24 boys in F.1A

Assume number of girls is X. then the number of boys is (1+1/3)X

So,

X + (1+1/3)X = 42
X = 18 = girl number

(1+1/3)*18 = 24 = boys number

Let a be the number of the girls.
4/3a+a=42
7/3a=42
a=18
The number of the girls is 18.

The number of the boys.
18+18x1/3
=24

The number of the boys is 24.

let there are y girls and y(1+1/3) boys in the class

y + y(1+1/3) = 42

y + y(4/3) = 42

(7/3)y = 42

y = 18

18 girls

18(1+1/3) = 24 boys