Let length = L m and width = W m. Then:-
LW = 350
2L + 2W = 90
from the above equation:-
L = (90 - 2W) / 2
Substituting for L in the first equation:-
W(90 - 2W) / 2 = 350
90W - 2W^2 = 700
2W^2 - 90W + 700 = 0
(2W - 70)(W - 10) = 0
W = 35 , 10
therefore L = 10, 35
Answer Length = 35m and width = 10 m