First you need to figure out how many balls are in the bag. There is 1 red, 3 blue, and 2x (x=# of blue balls) green balls. since there is 3 blue balls you double 3 to get how many green balls there are, which is 6. Then you do 1+3+6 to give you 10. Since there is 3 blue balls in a bag that consists of 10 balls, you have a probability of 3/10 or 30% or .3 to draw a blue ball.
