I'm not sure how to approach this perimeter word question

Question

The perimeter of a triangle plot of land is 2400 ft. The longest side is 200 ft less than twice the shortest. The middle side is 200 ft less than the longest side. Find the lengths of the three sides of the triangular plot.

Answer 1

Let L, M and S be the three sides, longest, middle and shortest respectively.

L + S + M = 2400

L = 2S - 200 -->  S = (L + 200)/2

M = L - 200

By substitution, we get

L + (L + 200)/2 + L - 200 = 2400

L = 1040

M = 840

S = 620