Please need help thank you

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.

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.