Answer :
When we have a number followed by the "%" it means that this number is divided in 100 parts, so we can represent it with a fraction as shown below:
[tex]63\text{ \%}=\frac{63}{100}[/tex]In order to determine the percentage of ice cream that was sold, we need to multiply the fraction above by the initial amount they had. This is done below:
[tex]\text{Sold}=\frac{63}{100}\cdot78=\frac{4914}{100}=49.14[/tex]They sold 49.14 gallons.