The perimeter of a rectangle is 24 inches and its length is 3 times its width. what are the length and the width of the rectangle? what the legnth and width

If you take the perimeter, 24, and cut it in half, you are left with the sum of two sides of the rectangle.  This is easier to manage. Now, make a list of numbers whose sum is 12.  I got 1+11, 2+10, 3+9, 4+8, 5+7, 6+6
The other part of the problem said that the length is 3 times its width.  look at the pairs of numbers, and is there a set the has one number that is three times larger than the other number in that same set?  Yes, 3 and 9. (9 is three times larger than 3)
So, the length of the rectangle is 9 inches and the width is 3 inches.