There are 15 students volunteering for a project. Some of them are freshmen and some are sophomores. Sophomores have volunteered 2 hours each and freshmen have volunteered 3 hours each with a total of 40 hours volunteered. Try to write a system of equation store present this situation and then solve the system.

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.

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

Simplify. 3(4+4x) (type your answer in with no spaces)