Answer
8 mi by 15 mi
Work Step by Step
x=length
$w=x-7$
$a=120$
$a=w*x$
$120 = x*(x-7)$
$x^2-7x=120$
$x^2-7x-120=0$
$x^2-15x+8x-120=0$
$x(x-15)+8(x-15)=0$
$(x-15)(x+8)=0$
$x-15=0$
$x=15$
$x+8=0$
$x=-8$ (invalid answer since we can't have a negative length)
$x=15$ (length)
$w = 15-7$
$w=8$
