Determine P(5 ≤ X ≤ 8)

Answer 1

You need the mean and the standard deviation (stndDev)

zMin = (5 - mean)/ stndDev

zMax = (8 - mean)/ stndDev

Then do

Prob ( z < zMax) - Prob( z < zMin) using your software

or the normal distribution table.

Otherwise the answer is zero because

Prob ( z < 8) = 1 and Prob (z < 5) = 1, so

Prob( 5 < z < 8) = Prob ( z<8) - Prob (z < 5) = 1-1 = 0