A car salesman has 9 used cars for sale. They have a mean price of $3000. What is the total price of all 9 cars? Please help I don't understand!! -thanks

Could somebody me with this radical simplification?

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters

The table below shows the function f. determine the value of f(3) that will lead to an average rate of change of 19 over the interval [3, 5]. a. 32 b. -32 c. 25 d. -25