The following data represent the flight time (in minutes) of a random sample of seven flights from one city to another city. 287, 270, 260, 266, 257, 264, 258 compute the range and sample standard deviation of flight time

The range is found by subtracting the highest and lowest values:
287-257=30.
To find the standard deviation, we must first find the mean.  That is found by adding together all of the data and then dividing by the number of data points.  The sum of the data is 1862.  Divide this by 7 (the number of data points) and the mean is 266.
Now we subtract each data point from the mean.  We square this number, average these together and find the square root:
287-266=21
270-266=4
260-266=-6
266-266=0
257-266=-9
264-266=-2
258-266=-8