Twelve more than half of a number is equal to the number

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.

The data set represents the ages of players in a chess club. 27, 34, 38, 16, 22, 45, 54, 60. what is the mean absolute deviation of the data set?

There are a total of 75 students in the robotics club and the science club. the science club has 11 more students than the robotics club. how many students are in the science club?