We need the perimeter of the window for framing
The window is in the shape of a rectangle with the height of

feet and width of

. The diagram of the shape is shown below
The perimeter of a shape is obtained by adding up the length of all the sides that form the shape.
The perimeter of the window is

=
We have two whole numbers 18 and 12 and two fractions

and

Adding the two fractions that have different denominator

, which is an improper fraction which we can change into a mixed number

So the perimeter of the window is
and the length of wood needed for the frame is

feet
Its E...........................................
12,14,16
You reduce similar terms ("n" and numbers) then you just simplify the equation and kind of guess the even numbers that equal 42 based on your answer (12)