Answer: 24, 24, 47
Explanation:
In order to form a triangle, the sum of two sides must be GREATER than the third side for all combinations.
a + b > c & a + c > b & b + c > a
23 + 28 = 51 which is NOT greater than 55
15 + 30 = 45 which is NOT greater than 45
8 + 17 = 25 which is NOT greater than 25
24 + 24 > 47 & 24 + 47 > 24 & 24 + 24 > 27
all combinations are true so these side lengths can form a triangle