4/18
With a six-sided die and 3 marbles there are 18 different outcomes.
(6 numbers • 3 marbles = 18 outcomes)
1/2 of the die is even (2,4,6) so that’s already a 3/6 chance of getting an even number. But since there is only one red marble there is a 1/3 chance of picking it. 3+1=4. 4/18