Percentage increase is 225%.
$\text{% increase} = \dfrac{ \color{red}{ \text{final value} } - \color{blue}{ \text{initial value} } }{ \color{blue}{ \text{initial value} } } \times 100$ | $$ \begin{aligned} \color{red}{ \text{final value} } &= 26 \\[1.5em] \color{blue}{ \text{initial value} } &= 8 \end{aligned} $$ |
$\text{% increase} = \dfrac{ \color{red}{ 26 } - \color{blue}{ 8 } }{ \color{blue}{ 8 } } \times 100 $ | |
$\text{% increase} = 2.25 \times 100 $ | |
$\text{% increase} = 225 \% $ |