Answer:
300 yards
Explanation:
You want to find the actual width of a rectangle whose length is 400 yards and whose map width and length are known.
Setup
The map dimensions and the actual dimensions are proportional:
(actual width)/(actual length) = (map width)/(map length)
actual width / (400 yd) = (6 in)/(8 in)
Solution
Multiplying the equation by 400 yd, we get ...
actual width = (400 yd)(6/8) = 300 yd
The width of the actual park is 300 yards.