Answer :

kimono
If the perimeter is 26, and the width is 4, then add 4 twice, to get 8. Then subtract 8 from 26 to then get 18, you have two lengths, so divide 18 by 2. Your answer is 9.

To check add  4+4+9+9 = 26.

hope it helped! :)
apologiabiology
perimiter of a rectangle=legnth +legnth +width+width
assuming that the door is a normal door in that it is a rectangle
width=4

perimiter=26
26=legnth +legnth+4+4
26=legnth+legnth+8
subtract 8 from both sides
18=legnt +legnth
divide by 2 ( since 2 legnths)
9=legnth

it is 9 feet tall