Question

I'm a bit confused on how to get x, the example doesn't make sense either.

Answer 1

We know that A=l*w and we also know that these two rectangles have to have the same area. This means we set the two area formulas equal to each other:
$(x)(12)=(16)(x-2)$
$12x=16x-32$
$-4x=-32$
$x=8$