Z=1.5 in this case, 0.933 should be the probability that X is less than 100, since you want greater than, you’d do 1 - .933. If the mean is at 85 and the standard deviation is relatively small (10) a good check would be to see if your answer makes sense. Since you’re looking for a number above the mean, it should be less than 50% as your answer (the normal distribution is symmetrical around the mean)