Final answer:
The fraction of the marbles that are white when the ratio of red to white marbles is 5 to 4 is a. 4/9.
Step-by-step explanation:
To find what fraction of the marbles were white when the ratio of red marbles to white marbles was 5 to 4, you first add up the total parts, which is 5 (red) + 4 (white) = 9 parts in total.
The fraction of the marbles that are white is represented by the 4 parts out of the 9 total parts, which gives us the fraction 4/9. Therefore, the fraction of the marbles that are white is 4/9.