I need help with a probablity question.?

You have a 65% chance of pulling a blue marble from each bag. The chances of pulling 3 blue marbles is:

(13/20) * (13/20) * (13/20)

The chances of pulling a red marble would therefore be:

1 - (13/20)^3

1 - 2197/8000

(8000 - 2197) / 8000

5803/8000

0.725375

You have a roughly 72.5% chance of pulling at least one red marble

13/20 chance for blue on each go

(13/20)^3 = chance of getting 3 blue marbles, therefore the same as getting no red marbles

1 - (13/20)^3 = chance of getting atleast 1 red marble

1 - (13/20)^3 = 0.725375

p(at least one red marble) =

1 - p(all blue marbles) =

1 - (13/20)^3 =

1 - 2197/8000 =

5803/8000