(1) If we denote width as w and length as l, then:
w = (2/3)*l = 2l/3
(2) Area = l*w
864 = l*w
Now if we substitute the equation from (1) into (2) we get:
864 = l*(2l/3)
864 = 2l^2/3
2592 = 2l^2
l^2 = 1296
l = 36 ft
(Technically here we could have taken the positive or negative square root of 1296 but since l > 0 we will reject -36 ft as an answer and are left with + 36 ft)
