This questions is testing you on your knowledge of measurements of a set and some very simple arithmetic. It may look like you need to do complicated calculations related to standard deviation, but you don't.

If the mean is 8.1 and 1 SD = 0.3, then 1.5 SD = 0.45 (simply 1.5*0.3).

So, the range for 1.5 SD from the mean is 8.1 +/- 0.45, or:

7.65 <= x <= 8.55

Now we simply tally up how many of the 12 terms fall within that range; every term except 7.51 is a winner, so the correct answer is 11: choose (e).

Thank you so much Stuart! it looks so simple now