YOU WILL NEVER NEED TO CALCULATE IT
Instead, draw a curve and fill in percentages:
Must know the mean! or cant solve. If not given, cant solve.
Match average to center line (mean), also median and mode have to be center line
And find out from the numbers given, what the actual standard deviation numbers are (i.e x, 2x) are from that median number
 Sample or population std dev:

for a sample! otherwise its /n not /(n1)
 where n is number of elements in data set
 x is each element
 barx is the mean
so its the sum of the square of each element's deviation from the mean (to make it positive), divided by one less than the numbers in the set, all quantity squarerooted