How do you find the mean of the following set of numbers: 12, 14, 16, 12, 13?

The mean is $13.4$
the mean $\overline{x} = \frac{\sum {x}_{i}}{n}$
$\overline{x} = \frac{12 + 14 + 16 + 12 + 13}{5} = 13.4$
You can also do $\overline{x} = 12 + \frac{2 + 4 + 1}{5} = 12 + \frac{7}{5} = 12 + 1.4 = 13.4$