This problem requires a system of equations.
Let x be the length and y be the width.
xy = 980 x = 5y
Substitute 5y for x.
5y(y) = 980
5y² = 980
y² = 980/5
y² = 196
y = √196
y = 14 feet
Substitute 14 for y.
x = 5y
x = 5(14)
x = 70 feet
The length is 70 feet.