You can
put this solution on YOUR website! .
Let W be the width.
Then the length is L = 2W - 4, and the area is W*L = W*(2W-4).
Your equation is
W*(2W-4) = 286, or
W*(W-2) = 143.
You can solve this quadratic equation using the quadratic formula,
or you can mentally find decomposition of the number 143 into the product of two positive integers that differ by 2: 143 = 11*13.
Answer. W = 13 (the width); L = 2*W - 4 = 2*13-4 = 22 (the length).
Check. 11*18 = 286 square meters. ! Correct !