When you multiply 3 times 2.5 times 1.05 you'll get 7.875. Rounded to the tenth place you'll get 7.9 because the tenths place is the one right after the decimal point so look at that and the number right after, in this case 8 and 7. Since 7 is >5 you round the next number up. 8 changes to 9 and the answer 7.9
