[tex]\begin{gathered} We\text{ do } \\ increment=\frac{\text{ Final price}}{\text{ Initial price}}-1 \\ =\frac{500}{425}-1 \\ =\frac{100}{85}-1 \\ =\frac{20}{17}-1 \\ =\frac{3}{17} \\ \approx0.18 \\ \\ Thus\text{ the percent increase is }18\text{ \%} \end{gathered}[/tex]