Express the area of a square with side length 3xy2 as a monomial

Don't know how to find x given these segment lengths

Find an equation of the line perpendicular to the graph of 28x-7y=9 that passes through the point at (4,1)

For a science project, a high school research team conducted a survey of local air temperatures. based on the results of the survey, the found that the average temperatures were around 10 degrees higher than expected. this result was wrong. the trouble with the survey was that most of the locations were exposed to direct sunlight and located over asphalt or sand, which resulted in higher temperatures than normal. this is a classic example of an error in which phase of inferential statistics?