Can you help me with the Pre-Calculus word problem?

Question

Gretchen's garden measured 10 feet long by 12 feet wide. Gretchen decreased the length each side of the garden by the same amount and decreased the area by one third. By how many feet did Gretchen reduce each side of her garden?

 

A. 2 feet

 

B. 3 feet

 

C. 4 feet

 

D. 20 feet  

Answer 1

Let x be the amount that Gretchen reduced each side:

 

(10-x)(12-x) = (2/3)(120)

 

Solve for x.  You'll get two answers.  Only one of the answers makes physical sense.