At the store, you buy some pencils for $0.50 each and some pens for $1.50 each. you spend a total of $12 and purchase 16 items (pencils and pens only). (a) write and solve a system of equations that model the problem. show all your work. (b) how many of each type of writing utensil did you purchase? (write your answer in a complete sentence)

Ur environment is very sensitive to the amount of ozone in the upper atmosphere. the level of ozone normally found is 4.04.0 parts/million (ppm). a researcher believes that the current ozone level is not at a normal level. the mean of 2525 samples is 4.44.4 ppm with a standard deviation of 0.80.8. assume the population is normally distributed. a level of significance of 0.020.02 will be used. make the decision to reject or fail to reject the null hypothesis. answer tables