What does it mean when a problem asks for an expression

Lisa has three classes that each last 50 minutes. what is the total number of minutes of the three classes

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

Which of the following vectors are orthogonal to (2,1)? check all that apply