7 out of 24 is made by other companies because you need to find a common denominator for all of the numbers which is 24. 1/3 times 8 is 8/24, 1/4 times 6 is 6/24 and 1/8 times 3 is 3/24. Then add all of those fractions and you get 17 then subtract 24 by 17 to get 7 out of 24 as your fraction. Hope this helps!
