The length of a rectangle is 3 times the width. the permitted of the rectangle is 72ft find the dimensions of the rectangle

Lets set up the relationship of the length to width:

l = 3w

Using this, we can make all the variables the same by substitution:

2l + 2w = perimeter
2l + 2w = 72
2(3w) + 2w = 72
6w + 2w = 72
8w = 72
w = 9

The width is 9, to the length must be 9*3, or 27.

Hope this helped!