I'm not really sure how to go about solving this.

"Let a represent the amount of probability within 2.5 standard deviations of the norm. Find a."

I was thinking that since z is the number of standard deviations, that P(-2.5<z<2.5) and a is the area? From the standard normal distribution table 2.5=.4938. So 2(.4938)= .9876?