Type of percentage that compares the final and original amounts

What expression is equivalent to 1/2(2+3x-6)

An automated water dispenser fills packets with one liter of water on average, with a standard deviation of 5 milliliter. the manual says that after a year of operation the dispenser should be tested to see if it needs recalibration. a year later a number of filled packets are set aside and measured separately. it is found that the average packet now contains about 0.995 liters. does the dispenser need calibration? explain your answer.

Ben is three times as old as samantha, who is two years older than half of michel's age. if michel is 12. how old is ben?