first you set up the equation like this:
2l + 2w = p = 16w [the length (l) and the width (w) multiplied by 2 then added together equals the perimeter which is in turn equal to w*16 or 16w]
remove p from the equation since it is just there to help you set up the following equation:
2l + 2w = 16w
the problem also says that l = w+12 so substitute the l in the equation with w+12:
2(w+12) + 2w = 16w
simplify:
2w + 24 + 2w => 4w + 24 = 16w
then you isolate the width (bring the w to one side of the equation):
12w=24
divide each side by 12 to get w by itself and you find that w=24/12 or =2
then go add 12 to 2 to find the length (2+12=14)
as with any problem, you might want to check that the answer works completely, so plug both numbers into the original perimeter equation:
2(12) + 2(2)= p = 32
32 is 16 times more than 2 the width so the problem works.