Rosemary and Darwin are discussing how to find the value of -28 + 45. Rosemary says the value of -28 + 45 = -73. Darwin
says the value of -28 + 45 = 17.
Who is correct, and why?

An advertising firm has an old computer that can prepare a whole mailing in 6 hours. with the of newer model the job is complete in 2 hours. how long would it take the newer model to do the job alone?

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.

The holiday party will cost $160 if 8 people attend.if there are 40 people who attend the party, how much will the holiday party cost