Arectangular athletic field is three times as long as it is wide. if the perimeter of tje athletic field is 128 yards, what are the dimensions

The length of the field is 48 yard while the width of the field is 16 yards.

My Work/Reasoning:
Say that the width is "x" yards. 
The length of the field is three times longer than the width. 
The perimeter of the rectangle is 128 yards. 
To get the perimeter of a rectangle you multiply the sum of the length and the width by two. 
Then you follow order of operations and add x and 3x. 
Then you multiply. 
After that, you divide 8 on both sides to get the width (total) in yards. 
Then you divide that to get the width. 
Finally, to get the length of the field, you multiply the width of the field by three to get its length. 

If cheese is $4.40 per kilogram, you should pay .88

Where’s the problems ? ?