Can someone please do this math problem with process shown

here ...

let us suppose breadth of the room be x.

then, length = 2x

now ,the cost of plastering the floor is RS 1080 at rate of RS 15 per ...

hence

the area of floor{length *breadth} =1080/15

x*2x=72

or,2x^2=72

or,x=√(72/2)

hence, the value of x= 6m

(ie. breadth {x}=6. &. length {2x}=12)

again

we have ,

volume of the room (length *breadth*height)is 396m^3

12*6*height=396

72*height=396

height=396/72

hence , height=5.5

we know,

the area of 4 walls = 2( length+breadth)*height

=2(12+6)*5.5

=198

hence the cost of plastering 4 walls at the rate of RS 20 per SQ meter = 198*20=RS 3960