Myah has a coin purse that is filled with 24 dimes and quarters. She has $3.60 in all. How many dimes are there? Use the method of substitution to solve.

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.