$15.5 - $10.75 = $4.75
$15.50 represents 100%. To find the percentage that represents $4.75 we can use the next proportion:
[tex]\frac{15.5\text{ \$}}{4.75\text{ \$}}=\frac{100\text{ \%}}{x\text{ \%}}[/tex]Solving for x:
[tex]\begin{gathered} 15.5\cdot x=100\cdot4.75 \\ x=\frac{475}{15.5} \\ x=30.6\text{ \%} \end{gathered}[/tex]Petra applied a discount of 30.6% to the original price
