A z-score tells you how many standard deviations a point is from the mean.
[tex]z = \frac{x - mean}{std dev}[/tex]
Working backwards with this formula,
[tex]x = z*std dev + mean \\ \\ x = 1.3*3 + 12 \\ \\ x = 15.9[/tex]
So the data point is 15.9 and is 1.3 std deviations from the mean of 12.
Hope this helps.
