Both the mean and sum of values in a random sample have approximately normal distributions, provided the population distribution is reasonably symmetric or the sample size is large. Probabilities about means and sums can therefore be translated into probabilities relating to the standard normal distribution using z-scores and evaluated as areas under the standard normal density.
Read the following question carefully to identify whether the probability relates to a sample mean, the total of the sample values or a single sample value. The templates on the left can be used to help evaluate the parameters of the approximate normal distribution of a sample mean or total. Then use the templates on the right to evaluate z-scores and drag over the standard normal normal density to find the required probability.
Repeat with a few different questions until you are confident with the method.