Can you tell me how to solve this math/statistics problem?

I’ve had to miss school for 3 days because of pneumonia. I have a final tomorrow and I have no idea how to do this!

Here’s the question:

Three hundred people are surveyed about the time they spend exercising each day. Based on the results, the time they spend follows a normal distribution with a mean of 40 minutes and a standard deviation of 5.5 minutes. About how many people spend 40 minutes to 51 minutes exercising each day?

The answer is 143.

But I don’t know how to get that. My friend gave me the answers so I could figure out how to work it back.

I also need to know how to expand a binomial using Pascal’s Triangle. I learned how to do it, but I can’t remember because it was months ago.