We know that Perimeter = 2 times the Length + 2 times the Width
So, L = 2W - 10m, and P = 412m
Our equation becomes 2(2W -10m) + 2W = 412m
expanding the equation, we get 4W - 20m + 2W = 412m
which becomes 6W = 432m
W = 72m
therefore, L = 2W -10m = 2(72m) - 10m = 134m
Proof: P = 2L + 2W = 2(134m) + 2(72m) = 412m