a perimeter is made up of a length and width, obviously, so you can write that out algebraically as 2L+2W=P. Now, since the length is 6ft greater than 2 times the width, it can be written as 2W+6. If we plug our new L value in now, we would make the equation 2(2W+6)+2W=P. From here on out, you just gotta plug and chug.
2(2W+6)+2W=P
2(2W+6)+2W=384
4W+12+2W=384
6W+12=384
6W=372
W=62