On each of these it looks like you need to find the probability of getting a z score in between two values (the proportion of the curve between those values, in other words).

First, find the proportion between negative infinity and the larger z score. Then find the proportion between negative infinity and the smaller z score. Then, lastly, subtract the second proportion from the first, and you'll be left with the proportion in the "middle" (in between the scores).

In the first problem, the proportion between neg infinity and z=2.85 is 0.9978. The proportion between neg infinity and z=0 is 0.50, so we then subtract the second proportion from the first to get .9978 - .50 = .4978.

Follow this process for all three problems.

There is a post in our Examples section called "The Vaunted Normal Distribution" that covers this.