The length of a rectangle is 4 more than twice the width the perimeter is 28 what is the length

Perimeter = length + length + width + width
if the perimeter is 28, then:
28 = length + length + width + width

if you know that the length is 4 more than twice the width, then:
length = 4 + 2 x width
(using L as length, and w as width then: L = 4 + 2w)

if you substitute that back into the equation
28 = L + L + w + w
you should get

28 = 4 + 2w + 4 + 2w + w + w
combine the 4's and the ws 
28 = 8 + 6w
subtract both sides by 8
22 = 6w
divide both sides by 6
w = 3 2/3

Perimiter=2(legnt+width)
or
p=2(l+w)

l=4+2w
p=28
28=2(l+w)
subsitte 4+2w for l
28=2(4+2w+w)
28=2(4+3w)
28=8+6w
subtract 8 from both sdies
20=6w
divide by 6
20/6=w
aprox
3 2/3=3.666666
so 3 2/3=width