Answer:
1 red marble to 6 total marbles
Explanation:
There are 3 red marbles, and (10 + 5 + 3) total marbles.
There are 3 red marbles to 18 total marbles
therefore the ratio is 3 to 18 which can be simplified by dividing both sides of the ratio by 3
the ratio is 3/3 : 18/3 which is 1:6