A principal conducts a study to find the average age of all math teachers in a given high school by
recording all their ages.
What type of study is this?

experimental
observational
census
sample survey
simulation

What is the expression in factored form? -20x^2 - 12x a. 4x(5x+3) b. -4x(5x-3) c. -4(5x+3) d. -4x(5x+3)

Barney & noblet customers can choose to purchase a membership for $25 per year members receive 10% off all store purchases 1. how much would a member pay per year if he bought $50 worth of items each year? 2. write a slope-intercept equation that expresses how much a member pays per year using x to represent his purchases per year 3. how much would a member have to spend per year to pay off his membership fee?

Solve the following pair of equations for x and y: ax/b_ by /a= a +b; ax - by = 2ab