Determine the number of events that would result in a blue or red marble being chosen from a jar containing 10 red marbles, 12 green marbles, 8 yellow marbles, and 10 blue marbles.

There are 10 red marbles and 10 blue marbles in the jar, so there are a total of 20 marbles that are either blue or red.

Therefore, there are 20 events that would result in a blue or red marble being chosen from the jar.