Answer:
1 in 5, or 20%
Explanation:
If there are 5 yellow balls, 3 blue balls, and 2 red balls, there are 10 balls in total. Since there are two red balls, and there's an equal chance of you picking any of the balls, there is a 2 in 10 chance of you picking a red ball. 2/10 can be simplified to 1/5, which equals 20%.