The bag could contain any positive multiple of three marbles such as 3, 6, 9, 12, and so forth, ensuring an equal number of red, blue, and yellow marbles, that is if there are n marbles, then each colour will be n/3.
The equal distribution of red, blue, and yellow marbles implies a multiple of three. Let's denote the number of marbles as 'n.' Each colour constitutes n/3 marbles.
To maintain an equal number, the total number of marbles 'n' must be divisible by 3. For instance, if there are 9 marbles, each colour has 3 marbles (9/3). This pattern persists for any multiple of three.
Therefore, the bag could contain 3 marbles, 6 marbles, 9 marbles, and so on, ensuring the distribution of red, blue, and yellow marbles remains balanced.
In conclusion, the bag could contain any positive multiple of three marbles, guaranteeing an equal number of red, blue, and yellow marbles. Examples include 3, 6, 9, 12, and so forth.