Question 135710
There are 8 + 12 + 10 = 30 total marbles, 12 of which are orange.  So there are 12 ways that you can pick an orange marble out of 30 possible ways to pick a marble.  The probability is therefore {{{12/30}}}.  Probability is always the number of successful outcomes divided by the total number of possible outcomes.


So, for x number of trials, you would expect {{{(12/30)x}}} trials to result in an orange marble.  For 120 trials, {{{(12/30)120}}}.  All you need now is to do the arithmetic.