If you increase something by 80 percent, your multiplying it by 1.8. This goes the same way for 50 percent. If you multiply 1.8 by 1.5, you will get 2.7. Then convert 2.7 to increasing something by 170 percent. So the answer is 170 percent.
The mean should be 80.5. This means the average number of test scores is 80.5. The mean absolute deviation should be 15.5. This means the average of the values are less than the mean by about 15.5.
