If the tenths place, or the number right after the decimal point, is above 5. You add one to the ones place and set the tens place to 0. If the tenths place is below 5, you just set it to 0.
Ricardo has 2 cases with x number of games in each. This means 2x is the amount of video games in both. He gives away 4. He now has 2x-4 and has 10 left. This is 2x-4=10. Solve for x.