Question

A rectangular garden covers 16,000 ft2. Its length is 60 ft longer than its width.

Answer 1

The width is x 
The length is x+60 

so x(x+60) = 16000 

x^2 + 60x = 16000 

 
x^2 + 60x + 900 = 900+16000 

(x+30)^2 = 16900
  
x+30 = 130
 
x = 100

So your answer is 100.