Of the following, which one is an observational study?
a. asking people for their opinion on the taste of a new cereal
b. checking the effectiveness of a new headache medicine by giving one group the new medicine and one group acetaminophen
c. tracking the temperature in a city over a five year period measuring the average d. strength of a batch of metal by stressing some sample pieces until they deform

On new year's day, the average temperature of a city is 5.7 degrees celsius. but for new year's day 2012, the temperature was 9.8 degrees below the average. i) if a represents the average temperature on new year's day and 7 represents the temperature on new year's day 2012, what formula accurately relates the two values together? ii) what was the temperature on new year's day 2012? dt a 0.8 ii) - 4 1 degrees celsius da-t-98 ii) 59 degrees celsius 1) 7 = -9,8 11) 59 degrees celsius ii) l degrees celsius

Which inequalities can be used to find the solution set of the following inequality? check all that apply. |2x – 5| (2x – 5) (2x + 5) –(2x – 5) –(2x + 5)

Use the elimination method to solve the systems of equations. choose the correct ordered pair. 7x+4y=39