15. (3 points) There are 300 chess pieces in black and white. The black crow divides the black and white pieces into 100 piles, with 3 pieces in each pile. Among them, there are 27 piles with only $l$ white piece, 42 piles with 2 or 3 black pieces, and the number of piles with 3 white pieces is equal to the number of piles with 3 black pieces. Therefore, the number of white pieces among these chess pieces is $\qquad$.
【Solution】Solution: There is only one white stone, i.e., 1 white and 2 black, in 27 piles,
2 black or 3 black in total 42 piles, among which 2 black is already known to be 27 piles, so 3 black has: $42-27=15$ (piles), therefore, 3 white is also 15 piles,

Since there are a total of 100 piles, then 2 white and 1 black has: $100-27-15-15=43$ (piles),
Therefore, the total number of white stones is: $27 \times 1 + 15 \times 0 + 15 \times 3 + 43 \times 2 = 158$ (stones);
Answer: There are a total of 158 white stones.
The answer is: 158.