OK.... here we go....
The width is 8 less than the length, so that means: w = L - 8.
So, since the area of a rectangle is: A = L x W ...
Therefore, 48 = L(L - 8)...
48 = L^2 - 8L...
continuing from there .... you get width = 4 and length = 12
48 = 4 x 12 (and notice that the width is 8 less than the length)