Okay so lets set up our equation...
4 red marbles
5 blue marbles
So the odds are simply 5/9.
If he takes one blue out there is now 4 blues and 4 reds, So the odds of pulling a red now are 4/8 = 1/2.
All you need to do now is multiply the first 2 ratios together to get the combined odds. (5/9)(1/2) = 5/18
So your answer is 5/18
Hope this helped. Good luck!
