Given:
tip = 15%
Cost without tip = $25
The total amount charged would be:
[tex]=\text{ 115 \% of cost without tip}[/tex]Hence:
[tex]\begin{gathered} =\text{ }\frac{115}{100}\text{ }\times\text{ 25} \\ =\text{ 28.75} \end{gathered}[/tex]Answer: The total cost is $ 28.75