Jerome has 1/2 12 of the group’s video games at his house. Mario has 2/5 25 of the group’s video games at his house. What fraction of the group’s video games is either at Jerome’s house or Mario’s house?

What do you mean by 1/2 12?

If your qustion means:

Jerome has 1 / 2 of the group’s video games at his house. Mario has 2 / 5
of the group’s video games at his house.

What fraction of the group’s video games is either at Jerome’s house or Mario’s house?

then

1 / 2 + 2 / 5 = 5 / 10 + 4 / 10 = 9 / 10 = 90 / 100 = 90%

Therefore, 9 / 10 = 90 % of the group's video games are either at Jerome or Mario's house.

By the way, most of us does not give real name on this site.

My nick mean "Man from Bosnia" and that's not my real name.

but thats not a fraction

no he means 9/10 when he says 90%

To find the fraction of the group's video games that are either at Jerome's house or Mario's house, we need to add the fractions of games they have separately.

First, let's calculate the fraction of games at Jerome's house:
Jerome has 1/2 * 12 = 6 games at his house.

Now, let's calculate the fraction of games at Mario's house:
Mario has 2/5 * 25 = 10 games at his house.

To find the total fraction, we add the fractions:
6 games + 10 games = 16 games.

Now, we need to express this total as a fraction of the group's video games. Let's find the total number of video games in the group:
12 games + 25 games = 37 games.

Therefore, the fraction of the group's video games that are either at Jerome's house or Mario's house is 16/37.