Answer: 7 red marbles.
Explanation:
Since we are given the information that there are only red marbles and blue marbles in the bag and that the probability of randomly choosing a red marble is 1 /9 while there are 63 marbles in total.
Then the number of red marbles will be:
= 1/9 × 63
= 7
There are 7 red marbles
The number if blue marbles will be:
= 63 - 7
= 56 blue marbles