I need help plz

Ineed asap.i cant understand this question i need someone to me right away

Evaluate the expression for the given value of the variable 7a - 4a for a =8

The annual snowfall in a town has a mean of 38 inches and a standard deviation of 10 inches. last year there were 63 inches of snow. find the number of standard deviations from the mean that is, rounded to two decimal places. 0.44 standard deviations below the mean 2.50 standard deviations below the mean 0.44 standard deviations above the mean 2.50 standard deviations above the mean