If I read this correctly, you are looking for P(67 < X < 70) = P(X < 70) - P(X < 67). You have calculated these values above so the next step is to plug them in.
height of students is normally distributed
Mean = 67
standard deviation = 4
what portion of students that are over 67 inches tall are also under 70 inches tall?
I get a z value of .5 for 67 inches and .9332 for 70 inches
If I simply divide the z value of .9332 by .5 I get 1.8664, which is obviously wrong because it is more than 1.
Would the correct answer be:
(.9332 - .5000) / .5000