Please help me I would be really grateful :D

John bought 5 lemons and used 2 of them for a salad how much did he use for.a salad . he used % of the lemons.

The equation x2 – 1x – 90 = 0 has solutions {a, b}. what is a + b?

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.