I don't understand 6k-6k+8-12k

Alaptop computer is purchased for $1350 . after each year, the resale value decreases by 30% . what will the resale value be after 5 years?

Elizabeth is using a sample to study american alligators. she plots the lengths of their tails against their total lengths to find the relationship between the two attributes. which point is an outlier in this data set?

At oaknoll school, 90 out of 270 students on computers. what percent of students at oak knoll school do not own computers? round the nearest tenth of a percent.