From the statement, we know that:
• the tip is 25% of the pre-tax amount,
,• the pre-tax amount is $3.12.
So the amount of the tip is:
[tex]\text{ TIP }=25\%\times\text{ pre-tax amount }=\frac{25}{100}\times\text{ \$3.12}=\text{ \$0.78.}[/tex]AnswerThe tip was $0.78.