SOLUTION: The number of chocolate chips in an​ 18-ounce bag of chocolate chip cookies is approximately normally distributed with a mean of 1252 chips and standard deviation 129 chips.

How are you supposed to do this? Are you supposed to do it manually, or use the TI-83/84 calculator?
Let me START you off/Get you going with a)


MANUALLY
Determine probability of SMALLER VALUE (1,000, in this case)
Using: , where:   = 1,000
                             = 1,252
                             = 129

 then becomes: 
A Z-score of - 1.95 = .0256


Determine probability of LARGER VALUE (1,500, in this case)
Using: , where:   = 1,500
                             = 1,252
                             = 129

 then becomes: 
A Z-score of 1.92 = .9726


The probability that a randomly selected bag contains between 1,000 and 1,500 chocolate chips: 

USING THE TI-83/84 CALCULATOR

Select:    2nd VARS → DISTR

           CHOICE 2: normalcdf

           normalcdf(1000,1500,1252,129)

           Press: Enter

You should get: , which is the probability that a randomly selected bag contains between 1,000 and 1,500 chocolate chips.