Let the stones of each piles be x, y and z respectively.
thus, x + y + z = 376
x=x
y = x + 24
z= 2y = 2(x+24)
This becomes x + x + 24 + 2(x+24) = 376
= 4x + 24 + 48 = 376
= 4x + 72 = 376
Thus, 4x = 304
Thus, x = 76
and y = 76 + 24 = 100
and z = 2 x 100 = 200
Thus, first pile has 76 stones, second pile has 100 stones and third pile has 200 stones