Chapter 6 - Percent - Review Exercises - Page 469: 30

18.2%

$\frac{Part}{Whole}=\frac{Percent}{100}$ Whole = 4320 Part = (increase in sales) = 5107 - 4320 = 787 $\frac{787}{4320}=\frac{percent}{100}$ $Percent = 100\times\frac{787}{4320} = 18.21$ Sales increased by 18.21$\approx$ 18.2%