The length of a rectangular piece of steel in a bridge is 3 meters less than double the width. the perimeter of the piece of steel is 24 meters. find the length of the piece of steel. find the width of the piece of steel.

Length = 2×width -3
or
L = 2w - 3

perimeter = 24 meters
or
p = 24m

p = 2L + 2w
or
24 = 2(2w-3) + 2w ( Remember L = 2w +3)

24 = 4w -6 +2w
24 = 6w + 6
24 - 6 = 6w
18 = 6w
18/6 = w
3 = w

Now that we know ,w, we can find L.

p = 2L + 2w
24 = 2L +2(3)
24 = 2L + 6
24 -6 = 2L
18 = 2L
18/2 = L
9 = L

Now, we can check if the answer makes sense.

p = 2L + 2w
24 = 2(9) + 2(3) (L = 9 & w =3 )
24 = 18 + 6
24 = 24

the answer checks!

Whose mistake? can you give more details to what the question is asking?