Hello, thank you for taking the time to post your question!
In each of these cases you want to use the underlying process of computing the Z score using the formula
Z = (x – mean) / (standard deviation)
then using either a normal table or technology in order to convert that value over into a probability.
When I follow that process for this set of information I get
0.6306 for part (a) and 0.8413 for part (b)
I hope that helps! Feel free to reach out if you have any questions beyond that or want to go over the calculations in more detail :)
