The formula to find the area of the walls of a rectangular room is a=2h (l+b), h is wall height, l is room length, and b is room breadth. the area of doors and windows are ignored.
question - using the formula find the wall area if the room length is 8m, breadth is 6m and height is 2.5 m.
sorry but i have no clue : (

Problems are very often written in a confusing way. This one couldn't possibly have been
written any more clearly.  Sooner or later, you have to stop telling yourself that you have
no clue, settle down, and carefully read the words that are right there on the page.

I'll tell you one more detail that's not in the problem:  "breadth" means "width".
 
Now.  The problem clearly tells you all of these things, in this exact order:

=>  Area of the walls = (2 x height) x (length + width)

=>  length = 8m
=>  width = 6m
=>  height = 2.5m 

Is there a reason you can't take the numbers for length, width, and height,
and write them in the formula for the area ?  Do I have to do all the work ?

Area = (2 x height) x (length + width)

Area = (2 x 2.5m ) x ( 8m    +   6m  )

Do the arithmetic inside the parentheses:

Area = (    5m     ) x (     14m          )

Do the multiplication:

Area = 70 m² .

You will never see a problem that comes any closer to answering itself for you.