Michael gave 2/5 of his marbles to his sister. he then divided the remainder equally among his 3 friends. if each of his friends receives 12 marbles, how many marbles did michael have at first?

The average number of vehicles waiting in line to enter a parking lot can be modeled by the function f left parenthesis x right x squared over 2 left parenthesis 1 minus x right parenthesis endfraction , where x is a number between 0 and 1 known as the traffic intensity. find the rate of change of the number of vehicles waiting with respect to the traffic intensity for the intensities (a) xequals0.3 and (b) xequals0.6.