How do you know if there is three vertices?

According to the data set, where should the upper quartile line of the box plot be placed?

597008.439431 to the nearest thousand

Mr. jones determined that the equation y = 98 - 16/5 x could be used to predict his students' unit test scores, based on the number of days, x, a student was absent during the unit. what was the meaning of the y-intercept of the function? (by the way the 16/5 is a )