Sums, Subscripts and Superscripts test (LaTeX)

$${{\sigma }^{2}}=\frac{1}{N}\sum\limits_{i=1}^{N}{{}}{{\left( {{x}_{i}}-\bar{x} \right)}^{2}}$$

Sums, Subscripts and Superscripts test (Microsoft Office equation converted to jpeg)

$$r^2$$

$$25\%$$