Answer:
C7,3=7!( 3!)( 7−3)!= 7! I think tell me if I'm wrong?
-15x - 3y = 3
-15x - 3(5x-1) = 3 [input y]
-15x - 15x - 3 = 3 [distribute 3 over 5x and -1]
-30x - 3 = 3 [combine like terms]
-30x = 6 [add 3 to eliminate the negative]
x =

[divide by -30 to get x alone]
x =

[reduce the fraction]
Hopefully this is helpful enough to get you to your answer
I found width=13.72 ft and length=43.72 ft.
Call one dimension of the rectangle x, the other will be x+30
You want an area A=600 ft^2 but A=length x width=x*(x+30)=600
Rearranging you get:

solving this quadratic equation you get a negative solution and a positive one that gives your result.
The answer is -1
Hope this helps!