The time required to cook a pizza at a neighborhood pizza joint is normally distributed with a mean of 12 minutes and a standard deviation of 2 minutes. find the time for each event. (round your answers to 2 decimal places.) a. highest 5 percent min. b. lowest 50 percent min. c. middle 95 percent min. to min. d. lowest 80 percent min.

Focus on "middle 95 percent min. to min" first.  The central 95% of the area under the std. normal curve represents -2 std. dev. up to 2 std. dev.  We need to convert std. dev. here into the actual x (minute) values, using the z-score formula:
         x - 12
z =    Let this equal -2 first and find x; then let this equal 2, and find x
             2
                                        x - 12
x again:                  -2 =  =>  -4 = x - 12  => 8 = x
                                           2

This means, when we're considering the middle 95% of cases, the minimum cooking time is 8 minutes.  The max would then be 12+4 = 16 minutes.

Hope this helps you get started.  Try solving the other 3 parts.  Let me know if you need further help with this.