side one is 5 side two is 10 and the third side is 13. 28 is not divisible by three so if one side i 5 ft longer and another side is 8 ft longer then you add them 5+8=13 then subtract 13 from the perimeter 28-13=15 then divide 15 by 3 and get 5 5 5. add 5 (5+5) (5+8).
