Answer:
length = 30 feet and width = 20 feet
Explanation:
Let l is length and b is width of a rectangular yard. The area of a rectangle is given by :
A = lb ..(1)
A rectangular yard has a length that is 10 feet longer than the width.
length, l = 10+b ...(2)
ATQ,
Put the value of l in equation (1),

Width can't be negative. The width is 20 feet.
Put the value of b is equation (2),
l = 10+20
l = 30 feet
Hence, the length and width are 30 feet and 20 feet.