Answer:
2/15
Step-by-step explanation:
There is a 4/10 probability that she chooses blue the first time, but the second time it is a 3/9 chance because she didn't put the marble back so there are 9 marbles in total, 3 blue ones.
4/10 x 3/9 = 2/5 x 1/3 = 2/15
I hope this helps :)
Edit: Messed up the multiplication, whoops!
The common ratio is the multiplicity of -3
hope this helps