Answer:
The sides are 
6 inches, 8 inches and 10 inches 
 
Explanation: 
I'd suggest that the question should read 'The perimeter of a triangle is 24 inches. The longest side is 4 inches longer than the shortest side, and the shortest side is three-fourths the length of the middle side. How do you find the length of each side of the triangle?' 
Then the shortest side is 
6 
 and the longest side is 
10
I hope this helps :)