Answer:
3/10
or
30%
Explanation:
Since this is based off the first try or "draw", there is a 1/10 (10%) chance of choosing any of the marbles in the bag. We already know that there are 3 red marbles out of a total of 10 in the bag. 3/10 would represent this as amount of red marbles to the total amount of marbles in the bag. 3/10 as a percentage is 30%. Therefore, your chance of drawing a red marble first try is a 30% chance.
Hope this helps and have a nice day!