Which expression is equivalent to 7z + 7z?

What is a rational number between 9.5 and 9.7

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.

Need this asap if anyone can i would be very grateful. if you could show workings that would really