On a six-sided dice, each has a number between 1 and 6. What is the probability of throwing a 3 or a 5
.

2/6 which simplified is 1/3 33% chance

So there is 6 possible options when you throw the dice 1,2,3,4,5,6 there's one of each number the chances of throwing any of those numbers is 1/6 but since you have two options 3 and5 the chances of you getting a 3 or 5 is 2/6 because you are fine two numbers and there are 6 numbers in total on that dice