summer practice problems

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My son has some practice problems for the summer: he is 15. We don't get this one:

A tennis court has area of 312 yrd^2. If the length is 2 yards more than twice the width, find the dimensions of the court.

He understands the formula of A=lw , he and I just aren't sure how to figure the equation. Any help sure would be appreciated by both of us. :)
 
Let w=width
Let l=length
Therefore A=wl
It is given that l=2w+2

A=wl
312=w(2w+2)
312=2w^2+2w
0=2w^2+2w-312
0=2(w^2+w-156)
0=2(w-12)(w+13)
w=12, -13

Note: If he hasn't learned factoring a quadratic, he might not understand the above.

It's up to him from here. We are talking about a physical object so the width cannot be negative which means you can eliminate one of the two answers.
 
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