Explanation
Given: Leila purchased 21,5cm of wire for $17.20.
Required: To determine the unit price in dollars per centimeter.
This is achieved thus:
To determine the unit price per centimeter, we divide the cost by the length of wire as follows:
[tex]\begin{gathered} 21.5cm=\text{ \$}17.20 \\ \therefore1cm=\frac{\text{ \$}17.20}{21.5}=\text{ \$}0.80 \end{gathered}[/tex]Hence, the answer is:
[tex]\text{ \$}0.80\text{ }per\text{ }centimeter[/tex]