Question 43003
Let w = width

So length(l) is 2w+8

Perimeter of a rectangle is 2l + 2w
In this case:
2(2w+8)+ 2w = 64. multiply out bracket on left
4w+16+2w = 64  
6w+16 = 64  subtract 16 from both sides
6w = 48  divide both sides by 6
w = 8
Width of rectangle is 8 inches

Pete